Despicable people run away from mêlée (4)
I believe the answer is:
scum
'despicable people' is the definition.
(I've seen this before)
'run away from melee' is the wordplay.
'run' becomes 'r' (cricket abbreviation).
'away from' indicates named letters should be taken away.
'melee' becomes 'scrum' (both can mean a group of people fighting).
'scrum' with 'r' removed is 'SCUM'.
(Other definitions for scum that I've seen before include "Impurities floating on water, or despicable people" , "Dirt on a liquid's surface" , "worst kind of people" , "Impure film" , "Waste matter floating on the surface" .)