An age taken ascending stadium (5)
I believe the answer is:
arena
'taken ascending stadium' is the definition.
'arena' can be an answer for 'stadium' (eg a sports arena). I'm not sure about the 'taken ascending' bit.
'an age' is the wordplay.
'an' becomes 'a'.
'age' becomes 'rena' (I can't justify this - if you can you should believe this answer much more).
'a'+'rena'='ARENA'
Can you help me to learn more?
(Other definitions for arena that I've seen before include "Space for public events" , "Place of activity, especially conflict" , "Wembley, say" , "Circus ring" , "battlefieId" .)