Confusion surrounds informer operating illegally (6)
I believe the answer is:
pirate
'operating illegally' is the definition.
(I've seen this before)
'confusion surrounds informer' is the wordplay.
'confusion' becomes 'pie' (I've seen this in other clues).
'surrounds' means one lot of letters goes inside another.
'informer' becomes 'rat' (synonyms).
'pie' going around 'rat' is 'PIRATE'.
(Other definitions for pirate that I've seen before include "Teach, perhaps" , "plagiarist" , "Corsair" , "not officially circulated" , "Robber on the high scas" .)