An epoch reflected in entertainment venue (5)
I believe the answer is:
arena
'entertainment venue' is the definition.
(I've seen this in another clue)
'an epoch reflected' is the wordplay.
'epoch' becomes 'era' (synonyms).
'reflected' says the letters should be written backwards (letters reflected back).
'an'+'era'='anera'
'anera' written backwards gives 'ARENA'.
'in' is the link.
(Other definitions for arena that I've seen before include "Place for public events" , "Playing area" , "Stadium - battlefield" , "Amphitheatre's central space" , "domain" .)