Fine and kind of brill? (4)
I believe the answer is:
fish
'brill?' is the definition.
(brill is a kind of fish)
'fine and kind of' is the wordplay.
'fine' becomes 'f' (abbreviation in pencil classifications).
'and' says to put letters next to each other.
'kind of' becomes 'ish' (eg cheapish means kind of cheap).
'f'+'ish'='FISH'
(Other definitions for fish that I've seen before include "Trawler's catch" , "rock, perhaps" , "Aquatic creature; rail-joining plate" , "Aquatic vertebrate" , "Customer" .)