Work is nicest time for boffin (9)
I believe the answer is:
scientist
'boffin' is the definition.
(I've seen this before)
'work is nicest time' is the wordplay.
'work' indicates anagramming the letters.
'time' becomes 't' (abbreviation).
'is'+'nicest'='isnicest'
'isnicest' with letters rearranged gives 'scientis'.
'scientis'+'t'='SCIENTIST'
'for' is the link.
(Other definitions for scientist that I've seen before include "Chemist or physicist, for instance" , "Inset tics for this learned one" , "entomologist maybe" , "one in the laboratory" , "Eg, a chemist" .)