Female everyone has to ridicule — a scapegoat (4,3)
I believe the answer is:
'a scapegoat' is the definition.
(I've seen this in another clue)
'female everyone has to ridicule' is the wordplay.
'female' becomes 'f' (abbreviation).
'everyone' becomes 'all' (all people).
'has' means one lot of letters go next to another.
'to ridicule' becomes 'guy' ('guy' can be a synonym of 'ridicule').
(Other definitions for fall guy that I've seen before include "Dupe" , "Scapegoat" , "Aunt Sally" , "Patsy" , "who's not 18 [UPRIGHT]?" .)