Fish, good variety of tuna, given to a huge glutton (9)
I believe the answer is:
gargantua
'huge glutton' is the definition.
The definition suggests a singular noun which matches the answer.
'fish good variety of tuna given to a' is the wordplay.
'fish' becomes 'gar' (type of fish).
'good' becomes 'g' (abbreviation).
'variety of' indicates anagramming the letters.
'given to' is a charade indicator (letters next to each other).
'tuna' anagrammed gives 'antu'.
'gar'+'g'+'antu'+'a'='GARGANTUA'
Can you help me to learn more?
(Other definitions for gargantua that I've seen before include "one with huge appetite" , "Giant" .)