Part of a French sex appeal (4)
I believe the answer is:
unit
'part' is the definition.
(unit is a kind of part)
'a french sex appeal' is the wordplay.
'a french' becomes 'un' ('a' in French).
'sex appeal' becomes 'it'.
'un'+'it'='UNIT'
'of' is the link.
(Other definitions for unit that I've seen before include "Single person - group of people" , "Quantity chosen as standard, or individual thing" , "Subdivision of a whole" , "Piece of furniture" , "Individual thing; one" .)