Stalls, so both have to change (6)
I believe the answer is:
booths
'stalls' is the definition.
('booth' can be a synonym of 'stall')
'so both have to change' is the wordplay.
'have to change' is an anagram indicator (I've seen 'has to change' mean this).
'so'+'both'='soboth'
'soboth' with letters rearranged gives 'BOOTHS'.
(Other definitions for booths that I've seen before include "Small area, for voting say" , "Small shops, at a fair say" , "Small areas, for voting say" , "Small temporary stalls, for voting, say" , "Small temporary shops, at a market say" .)