Spot congregation getting energy for nothing (5)
I believe the answer is:
fleck
'spot' is the definition.
(synonyms)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for fleck that I've seen before include "Little spot" , "Small patch of colour/light" , "Streak or spot" , "Small patch of colour" , "A bit of colouring" .)