Fool, one notorious for nicking people's chips? (4)
I believe the answer is:
gull
'fool' is the definition.
(I know that fool is a more specific form of the action betray)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for gull that I've seen before include "Dupe - sea bird" , "A bird; to deceive" , "Seabird - fool" , "Cheat, hoax" , "Delude - seabird" .)