Talk about energy fraud (5)
I believe the answer is:
cheat
'fraud' is the definition.
(I know that cheat is a type of fraud)
'talk about energy' is the wordplay.
'talk' becomes 'chat' (I've seen this before).
'about' indicates putting letters inside.
'energy' becomes 'e' (physics symbol as in E=mch).
'chat' enclosing 'e' is 'CHEAT'.
(Other definitions for cheat that I've seen before include "Two-time" , "Deceitful person" , "rook" , "Fraud" , "shark" .)