Defence from boxer swinging both ways? (5)
I believe the answer is:
alibi
'defence' is the definition.
(defence given to police by a suspect)
'boxer swinging both ways?' is the wordplay.
'boxer' becomes 'Ali' (Muhammad Ali).
'swinging both ways?' becomes 'bi' (short for bisexual).
'ali'+'bi'='ALIBI'
'from' is the link.
(Other definitions for alibi that I've seen before include "Evidence of (or excuse for) being somewhere else at the time" , "Defence in court" , "in order to prove I was elsewhere" , "Story confirming innocence" , "Timely get-out" .)