Laughter about a scoundrel initially alleviating back pain (8)
I believe the answer is:
headache
'pain' is the definition.
(I know that headache is a type of ache)
'laughter about a scoundrel initially' is the wordplay.
'laughter' becomes 'hehe' ('hehe' is the sound of laughter).
'about' is an insertion indicator.
'scoundrel initially' becomes 'dac' (I can't justify this - if you can you should believe this answer much more).
'a'+'dac'='adac'
'hehe' placed around 'adac' is 'HEADACHE'.
'alleviating back' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for headache that I've seen before include "trial" , "Migraine" , "Cause of worry/trouble" , "Cause of worry or trouble" , "nasty problem" .)