Work until one, using tea as a sedative (6)
I believe the answer is:
opiate
'a sedative' is the definition.
(I've seen this in another clue)
'work until one using tea' is the wordplay.
I cannot really see how this works, but
'work' could be 'op' (abbreviation for opus) and 'op' is located in the answer.
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
an anagram of 'tea' is 'ate' which is located in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'as' acts as a link.
Can you help me to learn more?
(Other definitions for opiate that I've seen before include "Drug made from poppy" , "Does it ease pain" , "one soporific" , "Drug inducing a false sense of contentment" , "Narcotic drug" .)