Fool one holding drink (3)
I believe the answer is:
mug
'fool' is the definition.
(I know that fool can be written as mug)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for mug that I've seen before include "Drinking vessel; rob" , "simpleton" , "Large cup without a saucer" , "In slang, a person easily deceived" , "Gullible person" .)