Win over Barking aids Rotherham's case (6)
I believe the answer is:
disarm
'win over' is the definition.
(thesaurus)
'barking aids rotherham's case' is the wordplay.
'barking' indicates an anagram (I've seen this in other clues).
'case' means to remove the middle letters.
'rotherham' with its middle taken out is 'rm'.
'aids' with letters rearranged gives 'disa'.
'disa'+'rm'='DISARM'
(Other definitions for disarm that I've seen before include "Make less hostile, win over" , "Demilitarise" , "Make less angry or deprive of weapons" , "Remove weapons from" , "Abandon MAD" .)