Appointment held in Frenchman’s second home? (4-1-5)
I believe the answer is:
pied-a-terre
'second home?' is the definition.
(I've seen this before)
'appointment held in frenchman's' is the wordplay.
'appointment' becomes 'date' (synonyms).
'held in' means one lot of letters goes inside another.
'frenchman' 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 "Dwelling for occasional use" , "Small secondary flat or house" , "Small home kept for occasional use" , "bijou accommodation" , "Lodging kept for occasional use (French)" .)