British band thus shortened Autumn in New York (3,4)
I believe the answer is:
the fall
'new york' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'british band thus shortened autumn in' is the wordplay.
'british band' becomes 'he' (I can't explain this - if you can you should give a lot more credence to this answer).
'shortened' indicates taking the first letters.
'autumn' becomes 'fall' (synonyms).
'in' is an insertion indicator.
The first letter of 'thus' is 't'.
't'+'fall'='tfall'
'he' put into 'tfall' is 'THE FALL'.
Can you help me to learn more?
(Other definitions for the fall that I've seen before include "Lapse into sin < in season in Vermont" , "LITERATURE" .)