Ace grog brewed brings trouble (5)
I believe the answer is:
aggro
'trouble' is the definition.
(short for aggression)
'ace grog brewed' is the wordplay.
'ace' becomes 'a'.
'brewed' indicates anagramming the letters.
'grog' anagrammed gives 'ggro'.
'a'+'ggro'='AGGRO'
'brings' acts as a link.
(Other definitions for aggro that I've seen before include "Bovver!" , "Difficulties (sl.)" , "Slang for deliberate trouble-making" , "Difficulties (informal)" , "Problems and difficulties" .)