Oddly Tim's about to make mistake with alternative for violence (9)
I believe the answer is:
terrorism
'violence' is the definition.
(I have seen 'Political violence ' mean 'terrorism' so perhaps 'violence' could also mean 'terrorism')
'oddly tim's about to make mistake with alternative' is the wordplay.
'oddly' indicates an anagram.
'about' is an insertion indicator.
'to make mistake' becomes 'err' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'alternative' becomes 'or'.
'tims' is an anagram of 'tism'.
'err'+'or'='error'
'tism' placed around 'error' is 'TERRORISM'.
'for' is the link.
(Other definitions for terrorism that I've seen before include "Unauthorised violence for political ends" , "Action of revolutionaries" .)