Crossword Genius

Violently beating ill-wisher inside — how mad can you get? (13)

Ross

I believe the answer is:

horsewhipping

'violently beating' is the definition.

'ill-wisher inside how mad can you get?' is the wordplay.
'ill' indicates an anagram.
'inside' indicates putting letters inside.
'how mad can you get?' becomes 'hopping' (as in the phrase 'hopping mad').
'wisher' is an anagram of 'rsewhi'.
'rsewhi' placed into 'hopping' is 'HORSEWHIPPING'.

I've seen this clue in The Guardian.
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