Assignation in French chap's bijou accommodation? (4-1-5)
I believe the answer is:
pied-a-terre
'bijou accommodation?' is the definition.
(I've seen this before)
'assignation in french chap's' is the wordplay.
'assignation' becomes 'date' (an assigned meeting).
'in' means one lot of letters goes inside another.
'french chap' becomes 'Pierre' (common French name).
'date' inserted inside 'pierre' is 'PIED-A-TERRE'.
(Other definitions for pied-a-terre that I've seen before include "Lodging kept for occasional use (French)" , "bijou accommodation" , "Small home kept for occasional use" , "Small secondary flat or house" , "Dwelling for occasional use" .)