Part of quiche Lorraine left over! (4)
I believe the answer is:
role
'part' is the definition.
(eg a theatrical role)
'quiche lorraine left over' is the wordplay.
'over' says the answer is hidden in the clue (the clue contains or goes 'over' the answer).
'left' shows that the letters should be reversed in order.
'elor' is hidden within 'quiche lorraine'.
'elor' reversed gives 'ROLE'.
'of' acts as a link.
(Other definitions for role that I've seen before include "Part, portrayal" , "Function; part" , "Part in play, film etc" , "Duty" , "Stage part" .)