Eavesdrop, I wager, craftily (6)
I believe the answer is:
earwig
'eavesdrop' is the definition.
(both can mean to listen to someone secretly)
'i wager craftily' is the wordplay.
'craftily' indicates an anagram (I've seen this in other clues).
'i'+'wager'='iwager'
'iwager' is an anagram of 'EARWIG'.
(Other definitions for earwig that I've seen before include "Insect with pincer-like tail" , "Fork-tailed insect" , "flatterer" , "listen in?" , "Go in for eavesdropping" .)