Wine region right to improve (5)
I believe the answer is:
rhone
'wine region' is the definition.
(I've seen this in another clue)
'right to improve' is the wordplay.
'right' becomes 'r' (common abbreviation).
'to improve' becomes 'hone' (honing is a kind of improving).
'r'+'hone'='RHONE'
(Other definitions for rhone that I've seen before include "Current" , "River rising in Switzerland and flowing into the Mediterranean" , "Fr. river and wine" , "wherein runs rain in Arbroath" , "River at Lyons" .)