Disable cold water movement (7)
I believe the answer is:
cripple
'disable' is the definition.
(thesaurus)
'cold water movement' is the wordplay.
'cold water' becomes 'C' (symbol for the cold tap).
'movement' becomes 'ripple' (ripple is a kind of movement).
'c'+'ripple'='CRIPPLE'
(Other definitions for cripple that I've seen before include "Disable - lame person" , "Make lame" , "Incapacitate" , "damage" , "Sabotage" .)