Opposed to throwing a tin (4)
I believe the answer is:
anti
'opposed to' is the definition.
(anti means opposing something)
'throwing a tin' is the wordplay.
'throwing' indicates anagramming the letters (letters get thrown around).
'a'+'tin'='atin'
'atin' anagrammed gives 'ANTI'.
(Other definitions for anti that I've seen before include "Definitely not pro" , "Person opposed" , "One who is against (something)" , "Policy's opponent" , "Not favouring" .)