Untidy woman in low bar was first to drink litres (11)
I believe the answer is:
dishevelled
'untidy' is the definition.
('dishevelled' can be similar in meaning to 'untidy')
'was first to drink litres' is the wordplay.
'was first' becomes 'led'.
'to' says to put letters next to each other (I've seen this in other clues).
'drink litres' becomes 'dishevel' (I can't justify this - if you can you should give a lot more credence to this answer).
'led' after 'dishevel' is 'DISHEVELLED'.
'woman in low bar' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
(Other definitions for dishevelled that I've seen before include "Not well turned out" , "Rumpled" , "Tousled" , "Blowzy" , "ill-groomed" .)