Self-inflicted damage that hurt along with treatment (3,4)
I believe the answer is:
own goal
'self-inflicted damage that hurt along with treatment' is the definition.
'own goal' can be an answer for 'self-inflicted damage' (I've seen this before). I'm not sure about the remainder of the definition.
'self-inflicted damage that hurt along' is the wordplay.
I cannot really see how this works, but
an anagram of 'along' is 'ngoal' which is located in the answer.
'that hurt' could be 'ow' (exclamation of pain) and 'ow' is found within the answer.
No letters remain.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for own goal that I've seen before include "embarrassing error" , "that gives advantage to opponents" , "aids the opposition" , "Blunder penalising the perpetrator" , "Self-inflicted disadvantage, from soccer" .)