What may poison police, struggling without leadership (1,4)
I believe the answer is:
e coli
'leadership' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see a link between them that I don't see?
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for e coli that I've seen before include "An infection found in food and water" , "cause of ill-feeling" , "cause of serious complaint" , "Cause of internal problem" , "Common species of bacterium" .)