Had he a square garden? (7)
I believe the answer is:
madison
'square garden?' is the definition.
'madison' can be an answer for 'square' (I've seen this before). I am not certain of the 'garden?' bit.
'had he a' is the wordplay.
I cannot quite understand how this works, but
'had' could be 'd' (in contractions e.g. 'I'd', 'you'd' etc) and 'd' is present in the answer.
'he' could be 'maison' and 'maison' is present in the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for madison that I've seen before include "-- Avenue, New York's advertising district" , "James -, fourth president of the USA" , "dance?" , "US President - county with bridges" , "New York Avenue for advertising people" .)