Boil these bursting with energy (6)
I believe the answer is:
seethe
'boil' is the definition.
('seethe' can be a synonym of 'boil')
'these bursting with energy' is the wordplay.
'bursting with' is an anagram indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
'these' mixed up with 'e' can make 'SEETHE'.
(Other definitions for seethe that I've seen before include "Boil; fume with suppressed rage" , "Bubble away" , "Appear as if boiling" , "Boil; be intensely angry" , "'Boil, with anger perhaps (6)'" .)