Spruce up grand space (5)
I believe the answer is:
groom
'spruce up' is the definition.
(thesaurus)
'grand space' is the wordplay.
'grand' becomes 'g' ('G' can be a synonym of 'grand').
'space' becomes 'room' (room is a kind of space**).
'g'+'room'='GROOM'
(Other definitions for groom that I've seen before include "dress?" , "Tender of horses" , "Newly-wed; preen" , "Curry - husband-to-be" , "Stable hand" .)