Go round part of theatre (6)
I believe the answer is:
circle
This clue is a triple definition!
'go' is the first definition.
(circling is a kind of going)
'round' is the second definition.
(synonyms)
'part of theatre' is the third definition.
(seating area in a theatre)
(Other definitions for circle that I've seen before include "Geometric shape" , "Number of people bound together by similar interests - sound round" , "Closed plane curve" , "Dress -; Magic -" , "Theatre seating tier" .)