Housekeeper and wife in unit on top of restaurant (5)
I believe the answer is:
owner
'housekeeper' is the definition.
(someone who owns or keeps a house)
'wife in unit on top of restaurant' is the wordplay.
'wife' becomes 'w'.
'in' indicates putting letters inside.
'unit' becomes 'one' (synonyms).
'on top of' suggests taking the first letters.
The initial letter of 'restaurant' is 'r'.
'w' inserted into 'one' is 'owne'.
'owne'+'r'='OWNER'
'and' is the link.
(Other definitions for owner that I've seen before include "Legal possessor" , "The one in lawful possession" , "Possessor, proprietor" , "One who has something" , "Person with legal title to something" .)