Characters in EPA interested in result of the injury (4)
I believe the answer is:
pain
'the injury' is the definition.
(thesaurus)
'characters in epa interested in' is the wordplay.
'characters in' indicates the answer is hidden within the clue.
'PAIN' is hidden in the letters of 'epa interested in'.
'result of' acts as a link.
(Other definitions for pain that I've seen before include "Suffering, distress" , "Sensation of hurt" , "Hurt feeling" , "Annoying person" , "Physical discomfort" .)