By middle-age, is mature enough to see how brilliant this is (4)
I believe the answer is:
gold
'enough to see how brilliant this is' is the definition.
The definition suggests a singular noun which matches the answer.
'by middle-age is mature' is the wordplay.
'by' means one lot of letters go next to another.
'middle' means to look at the middle letters.
'is mature' becomes 'old' (associated in meaning).
The middle of 'age' is 'g'.
'g' put next to 'old' is 'GOLD'.
Can you help me to learn more?
(Other definitions for gold that I've seen before include "gift from a king" , "Thin sheet of precious metal" , "Au - metal" , "Woman after a man's money" , "bull's-eye" .)