A cop gets a switch for whipping boy (9)
I believe the answer is:
scapegoat
'whipping boy' is the definition.
('scapegoat' can be a synonym of 'whipping boy')
'a cop gets a switch' is the wordplay.
'switch' indicates anagramming the letters.
'a'+'cop'+'gets'+'a'='acopgetsa'
'acopgetsa' anagrammed gives 'SCAPEGOAT'.
'for' is the link.
(Other definitions for scapegoat that I've seen before include "Person taking blame for others" , "One who takes the blame for others" , "one carrying the can" , "Can carrier" , "Person blamed for the wrongdoings or mistakes of others" .)