Great excitement in Slough that may cause problems in Hackney (5,5)

'cause problems in hackney' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

'great excitement in slough that' is the wordplay.
I cannot quite see how this works, but
'excitement' could be 'fever' (fever is a kind of excitement) and 'fever' is located in the answer.
'slough' could be 'swamp' (I've seen this before) and 'swamp' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).

'may' is the link.

Can you help me to learn more?