Carpet unorthodox at rear in a church (9)
I believe the answer is:
axminster
'carpet' is the definition.
(thesaurus)
'unorthodox at rear in a church' is the wordplay.
'at rear' suggests the final letters (the letter at the rear or back of the word).
'in' is an insertion indicator.
'church' becomes 'minster' (minster is a kind of church**).
The final letter of 'unorthodox' is 'x'.
'a'+'minster'='aminster'
'x' placed into 'aminster' is 'AXMINSTER'.
(Other definitions for axminster that I've seen before include "something underfoot?" , "Carpeting" , "Devon town; carpet" , "West Country town" , "Type of carpet" .)