Holds back and delivers once more (8)
I believe the answer is:
reserves
This clue is a double definition.
'holds back' is the first definition.
(reserve can mean to keep or hold back)
'delivers once more' is the second definition.
('serves' is an answer for 'delivers' so perhaps 'reserves' is OK for 'delivers once more')
'and' is the link.
(Other definitions for reserves that I've seen before include "group of people for backup?" , "Books" , "Stockpiles" .)