Energy concentrated in anger? Make friends again (9)
I believe the answer is:
reconcile
'make friends again' is the definition.
'energy concentrated in anger?' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mci).
'concentrated' becomes 'conc' (chemical abbreviation).
'in' indicates putting letters inside.
'anger?' becomes 'rile' (I've seen this in other clues**).
'e'+'conc'='econc'
'econc' put inside 'rile' is 'RECONCILE'.
(Other definitions for reconcile that I've seen before include "accommodate" , "Show to be compatible" , "Square" , "Be on friendly terms again" , "Settle (a quarrel)" .)