Flat fruit consumed by Frenchman (4-1-5)
I believe the answer is:
pied-a-terre
'flat' is the definition.
(I've seen this before)
'fruit consumed by frenchman' is the wordplay.
'fruit' becomes 'date' (date is a kind of fruit).
'consumed by' means one lot of letters goes inside another (inserted letters get consumed).
'frenchman' becomes 'pierre' (common French name).
'date' placed within 'pierre' is 'PIED-A-TERRE'.
(Other definitions for pied-a-terre that I've seen before include "Dwelling for occasional use" , "bijou accommodation" , "Small home kept for occasional use" , "Lodging kept for occasional use (French)" , "Small secondary flat or house" .)