He's found among entomologists (3)
I believe the answer is:
tom
'he's' is the definition.
'among entomologists' is the wordplay.
'among' says the answer is hidden in the clue.
'TOM' can be found hidden inside 'entomologists'.
'found' is the link.
(Other definitions for tom that I've seen before include "Boy running off with pig" , "Man's name; male cat" , "queen's consort?" , "He is associated with Dick and Harry" , "What Dick Whittington had" .)