Organised ad? I must, for sports venue (7)
I believe the answer is:
stadium
'sports venue' is the definition.
(I've seen this before)
'organised ad? i must' is the wordplay.
'organised' indicates anagramming the letters.
'ad'+'i'+'must'='adimust'
'adimust' with letters rearranged gives 'STADIUM'.
'for' acts as a link.
(Other definitions for stadium that I've seen before include "Open-air sports venue" , "bowl?" , "Sports ground as for athletics" , "eg Yankee, Wembley" , "Venue for sporting events, concerts etc" .)