Energy reforms suit MEP (7)
I believe the answer is:
impetus
'energy' is the definition.
(thesaurus)
'reforms suit mep' is the wordplay.
'reforms' indicates anagramming the letters.
'suit'+'mep'='suitmep'
'suitmep' anagrammed gives 'IMPETUS'.
(Other definitions for impetus that I've seen before include "Moving force" , "Drive" , "Momentum, stimulus" , "influence" , "Incentive, stimulus" .)