Hill torn apart in deluge (7)
I believe the answer is:
torrent
'deluge' is the definition.
(synonyms)
'hill torn apart' is the wordplay.
'hill' becomes 'tor' (tor is a kind of hill).
'torn apart' becomes 'rent' (past tense of 'rend', to tear or rip).
'tor'+'rent'='TORRENT'
'in' acts as a link.
(Other definitions for torrent that I've seen before include "Overwhelming outpouring" , "Violently fast stream of water" , "Overwhelming deluge" , "Rapid stream" , "Overwhelming flow" .)