Lots of money raised for a gem is underwritten by young men (9)
I believe the answer is:
megabucks
'lots of money' is the definition.
'raised for a gem is underwritten by young men' is the wordplay.
I cannot quite see how this works, but
'a' is present in the answer.
an anagram of 'gem' is 'meg' which is located in the answer.
'men' could be 'bucks' (I have seen 'young men' mean 'bucks' so perhaps 'men' could also mean 'bucks') and 'bucks' is found within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for megabucks that I've seen before include "Many grand" , "Huge money" , "Loads of money" , "Vast sums of money" , "large sum of money" .)