Heal dog with energy (4)
I believe the answer is:
cure
'heal' is the definition.
(I know that heal can be written as cure)
'dog with energy' is the wordplay.
'dog' becomes 'cur' (both can mean a despicable person).
'with' is a charade indicator (letters next to each other).
'energy' becomes 'e' (physics symbol as in E=mcu).
'cur'+'e'='CURE'
(Other definitions for cure that I've seen before include "Restore to good health" , "Parish priest in France" , "Make better or preserve in salt" , "Restorative" , "Remedy, therapy" .)