Boxing ring takes an age to erect (5)
I believe the answer is:
arena
'boxing ring' is the definition.
(I've seen this before)
'an age to erect' is the wordplay.
'age' becomes 'era' (both can mean a long time).
'to erect' says the letters should be written backwards.
'an'+'era'='anera'
'anera' in reverse letter order is 'ARENA'.
'takes' acts as a link.
(Other definitions for arena that I've seen before include "Sphere of action" , "Olympic venue?" , "An era (anag.)" , "Ring; stage" , "Ring for contest" .)