Where Roman contests were seen some time back (5)
I believe the answer is:
arena
This could be a double definition.
'where roman contests were seen some time' is the first definition.
The answer is a location as well as being a singular noun. This is suggested by the definition.
'back' is the second definition.
(thesaurus)
Can you help me to learn more?
(Other definitions for arena that I've seen before include "Performance venue" , "Coliseum" , "Ring for contest" , "Area of endeavour" , "Scene of gladiatorial contest, perhaps" .)