Ruff (5)
I believe the answer is:
trump
'ruff' is the definition.
(I know that ruff can be written as trump)
This is the entire clue.
(Other definitions for trump that I've seen before include "Outplay" , "Card of designated top suit" , "This card has an advantage" , "Card from chosen suit in various card games" , "Playing card with designated added value" .)