Formal proposal concerning answer to problem (10)
I believe the answer is:
resolution
'formal proposal' is the definition.
'resolution' can be an answer for 'proposal' (I've seen this before). I am not certain of the 'formal' bit.
'concerning answer to problem' is the wordplay.
I cannot really see how this works, but
'concerning' could be 're' (both can mean on a particular topic) and 're' is found in the answer.
'answer' could be 'solution' (synonyms) and 'solution' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for resolution that I've seen before include "Timely statement of intent" , "Firm decision" , "Clarifying" , "Fixed determination" , "purpose" .)