Notes genius is strangely large (5)
I believe the answer is:
elgar
'notes genius' is the definition.
The definition suggests a singular noun which matches the answer.
'strangely large' is the wordplay.
'strangely' indicates anagramming the letters.
'large' with letters rearranged gives 'ELGAR'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for elgar that I've seen before include "Glare strangely at the English composer" , "Scorer" , "British composer, d. 1934" , "Nimrod composer" , "man of note" .)