Excess energy contained in stewed fruits (7)
I believe the answer is:
surfeit
'excess' is the definition.
(synonyms)
'energy contained in stewed fruits' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mc2).
'contained in' is an insertion indicator.
'stewed' is an anagram indicator.
'fruits' with letters rearranged gives 'surfit'.
'e' put inside 'surfit' is 'SURFEIT'.
(Other definitions for surfeit that I've seen before include "it's more than one needs" , "Overindulge" , "Fustier (anag)" , "Superabundance" , "Overindulgence" .)