Alter church, leading to endless wrath (6)
I believe the answer is:
change
'alter' is the definition.
(I know that alter can be written as change)
'church leading to endless wrath' is the wordplay.
'church' becomes 'ch' (common abbreviation).
'leading to' says to put letters next to each other (some letters go before or lead others).
'endless' means to remove the last letter.
'wrath' becomes 'anger' (synonyms).
'anger' with its last letter taken off is 'ange'.
'ch'+'ange'='CHANGE'
(Other definitions for change that I've seen before include "Coins of low value" , "Alter, modify" , "we vary our routine for one" , "Replace" , "Coppers, perhaps" .)