Kept back, being shy (8)
I believe the answer is:
reserved
I believe this is a double definition.
'kept back' is the first definition.
(to reserve an item is to keep it back for someone)
'shy' is the second definition.
(reserved can mean shy or timid)
'being' acts as a link.
(Other definitions for reserved that I've seen before include "Shy; booked" , "cool" , "Booked - reticent" , "Slow to show emotion" , "Slow to reveal opinions; kept by" .)