Execute badly (5)

I believe the answer is:

lynch

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'execute' is the definition.
(thesaurus)

I cannot understand how the remainder of the clue works.

(Other definitions for lynch that I've seen before include "String up illegally" , "Punish without trial" , "Judge and execute without the law" , "Kill without legal sanction" , "- - law (= mob violence)" .)

I've seen this clue in the Evening Standard.

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