An ulcer exploded with some energy (7)
I believe the answer is:
nuclear
'some energy' is the definition.
(nuclear energy is a kind of energy)
'an ulcer exploded' is the wordplay.
'exploded' indicates anagramming the letters.
'an'+'ulcer'='anulcer'
'anulcer' with letters rearranged gives 'NUCLEAR'.
'with' is the link.
(Other definitions for nuclear that I've seen before include "Relating to atomic cores" , "winter, sort of" , "one's immediate family?" , "sort of family" , "Type of reaction" .)