Rushes communists with energy (5)
I believe the answer is:
reeds
'rushes' is the definition.
(I've seen this in another clue)
'communists with energy' is the wordplay.
'communists' becomes 'reds' (red is a kind of communist).
'with' is an insertion indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
'reds' placed around 'e' is 'REEDS'.
(Other definitions for reeds that I've seen before include "Water plants" , "Music-makers" , "They vibrate to produce the sound of various musical instruments" , "Woodwind instruments" , "Tall slender grasses of wet areas" .)