Band cooked with tuna that's rich (8)
I believe the answer is:
abundant
'rich' is the definition.
(similar in meaning)
'band cooked with tuna' is the wordplay.
'cooked with' is an anagram indicator (letters cooked into a new form).
'band' with its letters mixed up with 'tuna' can make 'ABUNDANT'.
'that's' is the link.
(Other definitions for abundant that I've seen before include "Guardian spirit" , "Existing in large quantities, plentiful" , "full" , "Present in great quantity" , "Copious, profuse" .)