Soundly beat husband after wager in London borough (7)
I believe the answer is:
lambeth
'london borough' is the definition.
(I know that Lambeth is a London borough)
'soundly beat husband after wager' is the wordplay.
'soundly beat' becomes 'lam' (lam can mean to hit violently).
'husband' becomes 'h'.
'after' says to put letters next to each other.
'wager' becomes 'bet' (synonyms).
'h' put after 'bet' is 'beth'.
'lam'+'beth'='LAMBETH'
'in' is the link.
(Other definitions for lambeth that I've seen before include "Location of Archbishop of Canterbury's palace" , "London borough with palace and walk" , "Archbishop of Canterbury" , "South London area with palace" , "South London borough" .)