German Mrs, a cheat for the most part (4)
I believe the answer is:
frau
'german mrs' is the definition.
(I've seen this before)
'a cheat for the most part' is the wordplay.
'a cheat' becomes 'fraud' (fraud is a kind of cheat).
'for the most part' means to remove the last letter (most but not all of the letters).
'fraud' with its last letter taken off is 'FRAU'.
(Other definitions for frau that I've seen before include "German married woman" , "German form of Mrs" , "Wife abroad" , "half of Hockenheimring?" , "German woman's title" .)