Filthy liquid in vessel quaffed by pandit (8)
I believe the answer is:
sewerage
'filthy liquid' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'vessel quaffed by pandit' is the wordplay.
'vessel' becomes 'ewer' (ewer is a type of jug).
'quaffed by' indicates putting letters inside (inserted letters are drunk or quaffed by others).
'pandit' becomes 'sage' (I can't justify this - if you can you should give a lot more credence to this answer).
'ewer' inserted into 'sage' is 'SEWERAGE'.
'in' is the link.
Can you help me to learn more?
(Other definitions for sewerage that I've seen before include "For removal of surplus water" , "Waste matter carried away drains" , "Provision of drainage" , "System of drains to carry away waste" , "removal of waste matter" .)