Cheats out of a packet (6)
I believe the answer is:
sachet
'packet' is the definition.
(I've seen this before)
'cheats out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'cheats' anagrammed gives 'SACHET'.
'of a' is the link.
(Other definitions for sachet that I've seen before include "Scent bag - shampoo envelope" , "Small soft bag, containing perfumed powder perhaps" , "Small packet (of, eg, shampoo)" , "Small envelope-like container" , "Small sealed envelope" .)