Renounce green reforms surrounding energy (6)
I believe the answer is:
renege
'renounce' is the definition.
(I've seen this before)
'green reforms surrounding energy' is the wordplay.
'reforms' indicates anagramming the letters.
'surrounding' means one lot of letters goes inside another.
'energy' becomes 'e' (physics symbol as in E=mc2).
'green' with letters rearranged gives 'renge'.
'renge' enclosing 'e' is 'RENEGE'.
(Other definitions for renege that I've seen before include "Fail to follow suit at cards" , "Change one's mind" , "Fail to follow suit or fulfil a promise" , "Go back on an obligation" , "Withdraw" .)