One’s drink gulped by old profligate (10)
I believe the answer is:
dissipated
'profligate' is the definition.
(I know that profligate can be written as dissipated)
'one's drink gulped by old' is the wordplay.
I cannot really see how this works, but
'one's' could be 'is' (Roman numeral) and 'is' is found in the answer.
'drink' could be 'sip' (sipping is a kind of drinking) and 'sip' is found in the answer.
'gulped' could be 'ate' (I've seen this in another clue) and 'ate' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for dissipated that I've seen before include "Dissolute" , "Squandered - debauched" , "Degenerate" , "Overindulgent" , "wasted?" .)