Dope in tin foil (4)
I believe the answer is:
info
'dope' is the definition.
(I've seen this before)
'in tin foil' is the wordplay.
'in' indicates a hidden word.
'INFO' can be found hidden inside 'tin foil'.
(Other definitions for info that I've seen before include "Facts; knowledge gained" , "Latest" , "What's known" , "details" , "counsel?" .)