Table water in Yorkshire returned sample of bacterium (8)
I believe the answer is:
listeria
'bacterium' is the definition.
(I know that listeria is a type of eubacteria)
'table water in yorkshire returned' is the wordplay.
'table' becomes 'list'.
'water in yorkshire' becomes 'aire' (I can't justify this - if you can you should give a lot more credence to this answer).
'returned' says the letters should be written in reverse.
'aire' backwards is 'eria'.
'list'+'eria'='LISTERIA'
'sample of' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for listeria that I've seen before include "Dangerous food bacterium" , "food culture" , "Common pathogenic bacterium" , "Micro-organisms associated with food poisoning" , "Is it real? (anag) -- kind of food poisoning" .)