Restaurant has an endless series of female supporters at first (9)
I believe the answer is:
brasserie
'restaurant' is the definition.
(brasserie is a kind of restaurant)
'an endless series of female supporters at first' is the wordplay.
'an endless' means to remove the last letter.
'series' becomes 'set' (both can mean a group of things).
'of female' becomes 'rie' (I am not sure about this - if you are sure you should believe this answer much more).
'supporters' becomes 'bras' (a bra gives support to breasts).
'at first' says to put letters next to each other.
'set' with its last letter taken off is 'se'.
'se'+'rie'='serie'
'serie' after 'bras' is 'BRASSERIE'.
'has' is the link.
Can you help me to learn more?
(Other definitions for brasserie that I've seen before include "bar serving food" , "eating place" , "Caf" , "eatery" , "bar in Paris" .)