Square Garden? Cuckoo's working! (7)
I believe the answer is:
madison
'square' is the definition.
(I've seen this before)
'garden? cuckoo's working' is the wordplay.
I cannot really understand how this works, but
'working' could be 'on' and 'on' is located in the answer.
'cuckoo' could be 'mad' (I've seen this in other clues) and 'mad' is located in the answer.
The remaining letters 'is' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for madison that I've seen before include "dance?" , "James, fourth US president" , "United States president -- Wisconsin's capital" , "State capital of Wisconsin" , "4th president of the US - capital of Wisconsin" .)