Regular customer (6)
I believe the answer is:
patron
'regular customer' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for patron that I've seen before include "Saint" , "manager (13) [FRENCH]" , "One gives financial or other support, to an artist say" , "one of the regular customers" , "Sponsor or backer as of the arts" .)