Trouble as a horse runs over (5)
I believe the answer is:
aggro
'trouble' is the definition.
(I've seen this before)
'a horse runs over' is the wordplay.
'horse' becomes 'gg' (geegee or GG is a childish term for a horse).
'runs' becomes 'r' (cricket abbreviation).
'over' becomes 'o' (cricket abbreviation).
'a'+'gg'+'r'+'o'='AGGRO'
'as' is the link.
(Other definitions for aggro that I've seen before include "Problems and difficulties" , "Bovver!" , "Trouble; forceful behaviour" , "In slang, hassle or troublemaking" , "Nasty behaviour" .)