A particular church’s unusual roofing? (6)
I believe the answer is:
thatch
'unusual roofing?' is the definition.
(as in a thatched roof)
'a particular church's' is the wordplay.
'a particular' becomes 'that' (that one over there).
'church' becomes 'ch' (common abbreviation).
'that'+'ch'='THATCH'
(Other definitions for thatch that I've seen before include "Reed or straw roofing" , "Alternative to lead roof" , "Old-fashioned roofing material" , "Plant stalks as roofing material" , "Organic material for old rustic roof" .)