Which church has a natural roof covering? (6)
I believe the answer is:
thatch
'a natural roof covering?' is the definition.
(I've seen this before)
'which church' is the wordplay.
'which' becomes 'that'.
'church' becomes 'ch' (common abbreviation).
'that'+'ch'='THATCH'
'has' acts as a link.
(Other definitions for thatch that I've seen before include "Reed or straw roofing" , "Old roof covering for house" , "Old-fashioned roofing material" , "Alternative to lead roof" , "Old roofing material" .)