Attacker from South America, one coming in at an angle (9)
I believe the answer is:
assailant
'attacker' is the definition.
('assailant' can be a synonym of 'attacker')
'south america one coming in at an angle' is the wordplay.
'south' becomes 's' ('S' can be a synonym of 'south').
'america' becomes 'a' (common abbreviation - e.g. in organisation names).
'one' becomes 'i' (Roman numeral).
'coming in' is an insertion indicator.
'at an angle' becomes 'aslant' (I've seen this before).
's'+'a'+'i'='sai'
'sai' inserted inside 'aslant' is 'ASSAILANT'.
'from' is the link.
(Other definitions for assailant that I've seen before include "An attacker like mugger" , "who is on the offensive?" , "Who would tear into" , "Aggressor" , "One attacking another" .)