Eavesdrops on insects? (7)
I believe the answer is:
earwigs
I believe this is a double definition.
'eavesdrops' is the first definition.
(I've seen this before)
'insects?' is the second definition.
(earwig is a kind of insect)
'on' acts as a link.
(Other definitions for earwigs that I've seen before include "Elongated insects" , "Eavesdrops on the insects" , "Bugs" , "Insect with pincers" , "listens in furtively" .)