Doled out by Royal Engineers, or kept back? (8)
I believe the answer is:
reserved
'kept back?' is the definition.
(to reserve an item is to keep it back for someone)
'doled out by royal engineers' is the wordplay.
'doled out' becomes 'served' (to dole out is to serve up or distribute).
'by' means one lot of letters go next to another.
'royal engineers' becomes 'RE' (abbreviation).
'served' after 're' is 'RESERVED'.
'or' is the link.
(Other definitions for reserved that I've seen before include "Slow to reveal opinions; kept by" , "unforthcoming" , "Shy - set aside" , "Spoken for" , "Slow to show emotions" .)