Synopsis
The problem here is caused by trying to abbreviate a sentence in which there is a combination of an (adverb + adjective) and a noun/adjective compound (adjective with a noun complement) using the same adjective.
General Explanation
The structure that we are concerned with is one in which the meaning of the adjective ‘relevant’ is narrowed or made more precise. The poster has two alternatives with the same adjective and wishes to make it more concise by avoiding repetition.
The full form of this involves a following pronoun and noun:
…evidence relevant to (the) clinic and relevant to policy
which could be abbreviated
…evidence relevant to clinic and policy.
However he wishes to shorten this further by dispensing with the preposition. His suggestions incorporate two possibilities:
- Converting the noun to an adverb. In cases where this is possible, e.g. with two nouns like ‘strategy’ and ‘tactics’, one could write:
…strategically and tactically relevant considerations.
No hyphen is needed because ‘strategically’ and ‘tactically’ are unambiguously adverbs.
- Using the noun to make a compound noun+adjective. This is done where no adverb related to the noun exists, e.g. ‘dog’ and ‘cat’:
…dog- and cat-relevant medications.
Hyphenation is not obligatory, but is often desirable to remove false scent†. It is necessary in this case of applying the convention that the adjective can be omitted in a list, to make it clear that the noun, ‘dog’, is in a compound with the hyphenated adjective later in the sentence.
The Example in the Question
The general problem here is that the noun, clinic (or clinical practice etc.), has an associated adverb, clinically, but the noun, policy, does not (political hardly serves). Thus, I would say:
A. This is incorrect as ‘clinically’ is an adverb which is not intended to qualify ‘policy-relevant’, the only possibility in the sentence.
B. The use of ‘clinical-’ followed by ‘policy-relevant’ indicates ‘clinical-relevant’ evidence, and is probably what the poster means. It is therefore grammatically correct.
I, personally find this jars, first because I am old-fashioned and don’t like invented noun-adjective compounds (I doubt whether you will find them in Jane Austen), and second because it seems to indicate lack of linguistic sophistication to use ‘clinical-relevant’ when the adverb, ‘clinically’, exists. Further, ‘clinical’ is an adjective, not a noun like ‘policy’, so there is an inconsistent feel about the sentence. However this is just a matter of style and taste, not grammar.
C. ‘Clinical’ without the hyphen is correct if the poster just means ‘clinical evidence’, whereas I suspect he means ‘clinic(al)-relevant’. (Again my own prejudice is against ‘policy-relevant’.)
Possible stylistic improvements
- Keep the two-letter, one-syllable pronoun ‘to’:
There is a need for evidence that is relevant to both policy and the
clinic.
or
- As suggested by Edwin Ashworth, keep both the adverbial and compound construction but write them in full:
There is a need for both clinically relevant and policy-relevant evidence
or
- Modify the sentence by choosing an appropriate word related to policy that has an adjectival form. This may or may not be possible depending on context, but something like:
There is a need for both clinically and administratively relevant
evidence
My own preference would be 1 (as a member of The Society for the Preservation of Prepositions), and, as previously explained, I do not like the compound of 2.
In addition, commenting, @SvenYargs suggested a further way to make the sentence more concise: replace “There is a need for” by “We need”.
† False Scent
To quote from the Wikipedia entry: “In… A Dictionary of Modern English Usage Fowler uses the heading false scent to explain writing that causes the reader to second-guess: because the writer knows what is coming ahead, he may forget that his reader does not, and unwittingly ‘lay false scent’ by writing something ambiguous that can only be disambiguated later in the text…”
In noun+adjective compounds without hyphenation, false scent would be laid if there were a possibility of reading the noun as a noun and subsequently have to adjust to the fact that it was part of a combination. In this case, ‘clinical’ (as an adjective) does not lay false scent, but if ‘policy’ came first in the sentence, “There is a need for policy ” could be read as such, whereas the ‘need’ is in fact for ‘evidence’.