Place of worship where the French returned sailor (5)
I believe the answer is:
altar
'place of worship' is the definition.
(I've seen this before)
'the french returned sailor' is the wordplay.
'the french' becomes 'la' (one of the French words for 'the').
'returned' shows that the letters should be reversed in order.
'sailor' becomes 'tar' (tar can mean a sailor).
'la' backwards is 'al'.
'al'+'tar'='ALTAR'
'where' is the link.
(Other definitions for altar that I've seen before include "Focus of religious activity" , "Church focal point" , "Place for sacrifices" , "High table for religious ceremonies" , "Place of sacrifice" .)