Bishop to go on in the pulpit perhaps where there's something thorny? (7)
I believe the answer is:
bramble
'where there's something thorny?' is the definition.
(bramble bushes have thorns)
'bishop to go on in the pulpit perhaps' is the wordplay.
'bishop' becomes 'B' (abbreviation for bishop in chess).
'to go on in the pulpit perhaps' becomes 'ramble' (ramble as if preaching).
'b'+'ramble'='BRAMBLE'
(Other definitions for bramble that I've seen before include "Prickly hazard" , "Prickly plant yielding blackberries" , "Blackberry plant" , "Dog rose" , "Blackberry shrub" .)