Where you'll find classical sightseers hasten all over the place (6)
I believe the answer is:
athens
'where you'll find classical sightseers' is the definition.
The answer is a location as well as being a singular noun. This is suggested by the definition.
'hasten all over the place' is the wordplay.
'all over the place' is an anagram indicator.
'hasten' is an anagram of 'ATHENS'.
Can you help me to learn more?
(Other definitions for athens that I've seen before include "6 capital" , "Hasten to Greece" , "Capital of Greece" , "European capital city" , "Plato's birthplace" .)