Sporting venue taking an age to erect (5)
I believe the answer is:
arena
'sporting venue' is the definition.
(sports arena)
'an age to erect' is the wordplay.
'age' becomes 'era' (both can mean a long time).
'to erect' shows that the letters should be reversed in order.
'an'+'era'='anera'
'anera' backwards is 'ARENA'.
'taking' is the link.
(Other definitions for arena that I've seen before include "Sports or entertainment venue" , "Sit around here being entertained" , "park" , "Area of activity, boxing perhaps" , "combat zone" .)