Wise to (2,2)
'wise to' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for in on that I've seen before include "Wise to" , "Aware of secret" , "Privy to" , "Participating in - knowing about" , "Sharing with" .)
(Another definition for inon that I've seen is " Privy to".)