Mean Grinch regularly spoilt enchantment (5)
I believe the answer is:
magic
'enchantment' is the definition.
(thesaurus)
'mean grinch regularly spoilt' is the wordplay.
'regularly spoilt' indicates alternate letters (letters are removed or spoiled on a regular basis).
'mean'+'grinch'='meangrinch'
The alternate letters of 'meangrinch' are 'MAGIC'.
(Other definitions for magic that I've seen before include "Sprinkling of fairy dust" , "Entertainment at a children's party?" , "Spelling?" , "Prestidigitation" , "Wizardry - wizard!" .)