Cleric, fool in church producing split (8)
I believe the answer is:
crevasse
'split' is the definition.
(thesaurus)
'cleric fool in church' is the wordplay.
'cleric' becomes 'rev' (abbreviation for Reverend).
'fool' becomes 'ass' (ass is a kind of fool**).
'in' is an insertion indicator.
'church' becomes 'ce' (abbreviation for Church of England).
'rev'+'ass'='revass'
'revass' put inside 'ce' is 'CREVASSE'.
'producing' acts as a link.
(Other definitions for crevasse that I've seen before include "Deep fissure in a glacier" , "gap" , "Sever sac (anag)" , "Deep open crack as in glacier" , "Deep glacial fissure" .)