Referee, say, in game with sides conserving energy (8)
I believe the answer is:
whistler
'referee' is the definition.
(I've seen this before)
'in game with sides conserving energy' is the wordplay.
'in game' becomes 'whist' (whist is a card game. I am not sure about the 'in' bit.).
'with' says to put letters next to each other.
'sides' becomes 'LR' (abbreviations for left and right).
'conserving' means one lot of letters goes inside another.
'energy' becomes 'e' (physics symbol as in E=mch).
'lr' going around 'e' is 'ler'.
'whist'+'ler'='WHISTLER'
'say' is the link.
Can you help me to learn more?
(Other definitions for whistler that I've seen before include "American artist who painted his mother, d. 1903" , "He famously painted his mother" , "American painter, 1834-1903" , "He used canvas" , "referee" .)