With the treatment for the main trouble, get a positive result (8)
I believe the answer is:
manicure
'with the treatment for' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'main trouble get a positive result' is the wordplay.
'trouble' indicates anagramming the letters.
'get' is a charade indicator (letters next to each other).
'a positive result' becomes 'cure' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'main' is an anagram of 'mani'.
'mani'+'cure'='MANICURE'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for manicure that I've seen before include "Care of hands and nails" , "Cosmetic treatment for the hands" , "Cosmetic care of the hands" , "Grooming for 10, 17 and 18" , "Professional care for the hands" .)