Encourage burst of energy, fading at the end (4)
I believe the answer is:
spur
'encourage' is the definition.
(spur can mean to encourage)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for spur that I've seen before include "Egg on or goad as horseman might" , "slip road" , "Drive on" , "This provokes sudden movement!" , "Sharply pointed projection" .)