A sucker for a drink (5)
I believe the answer is:
straw
'a sucker' is the definition.
(something used to suck drinks)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for straw that I've seen before include "Dry stalks" , "Residue of threshed corn" , "Animal bedding" , "Warts (anag.)" , "What a sucker gets given" .)