Switch needs hammering in cylinder, briefly (7)
I believe the answer is:
reroute
'switch' is the definition.
(as in switching a route)
'hammering in cylinder briefly' is the wordplay.
'hammering' becomes 'rout' (both can mean a decisive defeat).
'in' indicates putting letters inside.
'cylinder' becomes 'reel' (eg a reel of film).
'briefly' means to remove the last letter.
'reel' with its last letter taken away is 'ree'.
'rout' placed inside 'ree' is 'REROUTE'.
'needs' is the link.
(Other definitions for reroute that I've seen before include "Send on different path" , "Send in alternative direction" , "Change direction" , "Divert" , "Send a different way" .)