Smarten up grand accommodation (5)
I believe the answer is:
groom
'smarten up' is the definition.
(as in grooming oneself)
'grand accommodation' is the wordplay.
'grand' becomes 'G' (G is short for ground as in a thousand).
'accommodation' becomes 'room' (eg a hotel room).
'g'+'room'='GROOM'
(Other definitions for groom that I've seen before include "fellow for the match" , "man to forge a partnership" , "Recently-married man" , "One who brushes up" , "Train, make ready" .)