'You have to watch this young wine' notice (4-3)
I believe the answer is:
must-see
'you have to watch this young' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'wine notice' is the wordplay.
'wine' becomes 'must' (I have seen 'Unfermented wine ' mean 'must' so perhaps 'wine' could also mean 'must').
'notice' becomes 'see' (notice can mean to spot or see).
'must'+'see'='MUST-SEE'
Can you help me to learn more?
(Other definitions for must-see that I've seen before include "Remarkable sight" , "Unmissable" .)