Be conscious of fine fish (4)
I believe the answer is:
feel
'be conscious of' is the definition.
(thesaurus)
'fine fish' is the wordplay.
'fine' becomes 'f' (abbreviation e.g. condition of old coins, books).
'fish' becomes 'eel' (eel is a type of fish).
'f'+'eel'='FEEL'
(Other definitions for feel that I've seen before include "Leg (of mutton/lamb)" , "Experience, perceive" , "Consider" , "impression" , "Perceive by touch" .)