Make fast returns on advance payment for foyer (8)
I believe the answer is:
anteroom
'foyer' is the definition.
('anteroom' can be a synonym of 'foyer')
'make fast returns on advance payment' is the wordplay.
'make fast' becomes 'moor' (mooring is a kind of making fast).
'returns' shows that the letters should be reversed in order.
'on' is a charade indicator (letters next to each other).
'advance payment' becomes 'ante' (I've seen this before).
'moor' written backwards gives 'room'.
'room' put after 'ante' is 'ANTEROOM'.
'for' is the link.
(Other definitions for anteroom that I've seen before include "where people can wait" , "Large waiting area" , "Small chamber leading to another" , "vestibule" , "Root name (anag) - lobby" .)