Southwark infirmary for men only? (4,8)
I believe the answer is:
Here is my best explanation:
'only?' is the definition.
Both the answer and definition are adjectives.
Perhaps you can see a link between them that I can't see?
'southwark infirmary for men' is the wordplay.
'southwark infirmary' becomes 'hospital' (I can't explain this - if you can you should give a lot more credence to this answer).
'for' says to put letters next to each other (I've seen this in other clues).
'men' becomes 'guys'.
'hospital' put after 'guys' is 'GUYS HOSPITAL'.
(Another definition for guys hospital that I've seen is "London medical teaching establishment".)