Something noteworthy to sit down and play (5)
I believe the answer is:
cello
'something noteworthy' is the definition.
I can't tell whether this definition defines the answer.
'sit down and play' is the wordplay.
'sit' becomes 'cell' (I can't justify this - if you can you should give a lot more credence to this answer).
'down' suggests deleting specific letters (to be down something is to be missing it).
'and' becomes 'n' (common abbreviation for 'and').
'play' becomes 'no' (no or noh is a type of Japanese theatre).
'no' with 'n' taken away is 'o'.
'cell'+'o'='CELLO'
'to' is the link.
Can you help me to learn more?
(Other definitions for cello that I've seen before include "Music-maker" , "Musical instrument like large violin held between legs" , "big fiddle?" , "Casals' instrument" , "10 [INSTRUMENT]" .)