Rock band, popularly, coming on board? That’s worth mentioning (8)
I believe the answer is:
quotable
'rock band popularly' is the definition.
I can't judge whether this definition defines the answer.
'on board? that's worth mentioning' is the wordplay.
'on' says to put letters next to each other.
'board?' becomes 'table' (both can mean food).
'that's worth mentioning' becomes 'quo' (I can't justify this - if you can you should believe this answer much more).
'table' after 'quo' is 'QUOTABLE'.
'coming' acts as a link.
Can you help me to learn more?
(Other definitions for quotable that I've seen before include "worth citing" , "worthy of mention" , "suitable for recall" .)