On reflection Val is hard but generous (6)
I believe the answer is:
lavish
'generous' is the definition.
('lavish' can be similar in meaning to 'generous')
'on reflection val is hard' is the wordplay.
'on reflection' shows that the letters should be reversed in order.
'hard' becomes 'h'.
'val' back-to-front is 'lav'.
'lav'+'is'+'h'='LAVISH'
'but' is the link.
(Other definitions for lavish that I've seen before include "Splendid" , "Generous, profuse" , "Abundant, generous" , "Sumptuously rich" , "Profusely generous" .)