Exotic insect is beginning to torment boffin (9)
I believe the answer is:
scientist
'boffin' is the definition.
(I've seen this before)
'exotic insect is beginning to torment' is the wordplay.
'exotic' indicates anagramming the letters.
'beginning to' indicates taking the first letters.
The initial letter of 'torment' is 't'.
'insect' is an anagram of 'scient'.
'scient'+'is'+'t'='SCIENTIST'
(Other definitions for scientist that I've seen before include "It's insect, strangely, this learned person knows about" , "`Tis nicest kind of specialist" , "Eg, a chemist" , "entomologist maybe" , "Inset tics for this learned one" .)