With no source of sugar, amrita is a poor drink (3,5)
I believe the answer is:
tia maria
'poor drink' is the definition.
'with no source of sugar amrita is a' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'amrita' is 'tiamar' which is within the answer.
'a' is present in the answer.
A single letter 'i' remains which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tia maria that I've seen before include "Coffee-flavoured rum drink" , "Coffee-flavoured Caribbean liqueur" , "Coffee flavoured liqueur" , "Rum-based coffee liqueur" , "drink is served?" .)