Cherish sinner - he's reformed (8)
I believe the answer is:
enshrine
'cherish' is the definition.
(I've seen this before)
'sinner he's reformed' is the wordplay.
'reformed' indicates anagramming the letters.
'sinner'+'he'='sinnerhe'
'sinnerhe' anagrammed gives 'ENSHRINE'.
(Other definitions for enshrine that I've seen before include "Preserve (something) in a form ensuring respect" , "Treasure" , "Hold sacred - protect" , "Inns here (anag.)" , "Preserve and cherish as in holy place" .)