Squid caught malaria at sea! (8)
I believe the answer is:
'squid' is the definition.
('calamari' can be a synonym of 'squid')
'caught malaria at sea' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'at sea' indicates an anagram.
'malaria' with letters rearranged gives 'alamari'.
(Other definitions for calamari that I've seen before include "Squid prepared as food" , "Battered squid rings" , "Mediterranean cooked squid" , "Dish of squid" , "Squid served as food" .)