Wager is about insects (7)
I believe the answer is:
earwigs
'insects' is the definition.
(earwig is a kind of insect)
'wager is about' is the wordplay.
'about' is an anagram indicator.
'wager'+'is'='wageris'
'wageris' anagrammed gives 'EARWIGS'.
(Other definitions for earwigs that I've seen before include "Elongated insects" , "Bugs" , "Eavesdrops on the insects" , "listens in furtively" , "Insect with pincers" .)