Endless arid zone, a state of the USA (7)
I believe the answer is:
arizona
'usa' is the definition.
The answer and definition can be both locations as well as being singular nouns.
Maybe there's an association between them I don't understand?
'endless arid zone a state of' is the wordplay.
'endless' means to remove the last letter.
'zone' becomes 'z'.
'a state of' becomes 'ona' (I am not sure about this - if you are sure you should believe this answer much more).
'arid' with its final letter taken off is 'ari'.
'ari'+'z'+'ona'='ARIZONA'
'the' is the link.
Can you help me to learn more?
(Other definitions for arizona that I've seen before include "Dry US state" , "US state containing the Grand Canyon" , "State of southern US" , "American state, capital Phoneix" , "US state, capital Phoenix" .)