Carpet unknown in a place of worship (9)
I believe the answer is:
axminster
'carpet' is the definition.
(I've seen this before)
'unknown in a place of worship' is the wordplay.
'unknown' becomes 'x' (algebra).
'in' is an insertion indicator.
'place of worship' becomes 'minster' (minster is a kind of place of worship).
'a'+'minster'='aminster'
'x' going into 'aminster' is 'AXMINSTER'.
(Other definitions for axminster that I've seen before include "something underfoot?" , "Carpeting" , "West Country town" , "Kind of patterned carpet" , "south-west town" .)