No explosive energy in runner (7)
I believe the answer is:
nominee
'runner' is the definition.
(I've seen this in another clue)
'no explosive energy in' is the wordplay.
'explosive' becomes 'mine' (e.g. a landmine).
'energy' becomes 'e' (physics symbol as in E=mc2).
'in' is an insertion indicator.
'mine' enclosing 'e' is 'minee'.
'no'+'minee'='NOMINEE'
(Other definitions for nominee that I've seen before include "someone to act for them" , "Candidate for office" , "No real owner" , "Person selected to seek election" , "Candidate - appointed person" .)