Old policeman with energy to become really angry (7)
I believe the answer is:
explode
'become really angry' is the definition.
I can't judge whether this defines the answer.
'old policeman with energy' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'policeman' becomes 'plod' (UK informal term for a police officer).
'with' is a charade indicator (letters next to each other).
'energy' becomes 'e' (physics symbol as in E=mcl).
'ex'+'plod'+'e'='EXPLODE'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for explode that I've seen before include "mushroom" , "Pop" , "Violently shatter" , "Go off with a bang" , "Detonate" .)