Move mountains: I’d upset church (8)
I believe the answer is:
displace
'move' is the definition.
(displacing is a kind of moving)
'mountains i'd upset church' is the wordplay.
'mountains' becomes 'alps' (alp is a kind of mountain).
'upset' shows that the letters should be reversed in order.
'church' becomes 'ce' (abbreviation for Church of England).
'alps'+'id'='alpsid'
'alpsid' backwards is 'displa'.
'displa'+'ce'='DISPLACE'
(Other definitions for displace that I've seen before include "Supplant" , "Shift" , "Oust" , "Remove from usual habitat" , "Succeed" .)