Triad warring with CIA in the sea (8)
I believe the answer is:
adriatic
'the sea' is the definition.
(Adriatic is an example)
'triad warring with cia' is the wordplay.
'warring with' indicates anagramming the letters.
'triad' with its letters mixed up with 'cia' makes 'ADRIATIC'.
'in' acts as a link.
(Other definitions for adriatic that I've seen before include "Sea to the east of Italy" , "Balkan-Italian sea" , "Part-Mediterranean" , "The drink" , "Sea between Italy and former Yugoslavia" .)