Giant tuna, gutted and canned? (5)
I believe the answer is:
titan
'giant' is the definition.
(titans are giant mythological creatures)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for titan that I've seen before include "Huge character" , "Atlas, say" , "Person of great strength - moon of Saturn" , "one of great importance" , "Taint in a great man" .)