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' shows that the letters should be reversed in order (letters reflected back).
'an'+'era'='anera'
'anera' back-to-front is '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" .)