She's a treasure to the master (5)
I believe the answer is:
gemma
'she's' is the definition.
Both the definition and answer are singular nouns.
Maybe there's a link between them I don't understand?
'a treasure to the master' is the wordplay.
'a treasure' becomes 'gem' (gem is a kind of treasure).
'to the master' becomes 'MA' (Master of Arts).
'gem'+'ma'='GEMMA'
Can you help me to learn more?
(Other definitions for gemma that I've seen before include "Bud" , "Girl's name" , "girl" .)