Standing for, say, about half an hour (7)
I believe the answer is:
stature
'standing' is the definition.
(stature is a kind of standing)
'say about half an hour' is the wordplay.
'say' becomes 'state' ('state' can be a synonym of 'say').
'about' means one lot of letters goes inside another.
'half an hour' becomes 'ur'.
'state' enclosing 'ur' is 'STATURE'.
'for' acts as a link.
(Other definitions for stature that I've seen before include "Size or standing" , "Person's natural height" , "Treat us (anag)" , "moral greatness" , "Importance earned through achievement" .)