Rocky peak split rushing water (7)
I believe the answer is:
torrent
'rushing water' is the definition.
(I've seen this before)
'rocky peak split' is the wordplay.
'rocky peak' becomes 'tor' (I've seen this before).
'split' becomes 'rent' ('rent' can be a synonym of 'split').
'tor'+'rent'='TORRENT'
(Other definitions for torrent that I've seen before include "Turbulent stream of water" , "A rushing stream of water" , "Heavy stream" , "'Flood, downpour (7)'" , "Overwhelming deluge" .)