A coach I have can be insulting (7)
I believe the answer is:
abusive
'be insulting' is the definition.
('abusive' can be a synonym of 'insulting')
'a coach i have' is the wordplay.
'coach' becomes 'bus' ('bus' can be a synonym of 'coach').
'i have' becomes 'ive'.
'a'+'bus'+'ive'='ABUSIVE'
'can' is the link.
(Other definitions for abusive that I've seen before include "Swearing, insulting" , "Rude, insulting" , "Extremely insulting" , "Reviling with coarse language" , "Insulting, foul-mouthed" .)