Carriage, they say, for spectators ... (4)
I believe the answer is:
gate
'spectators' is the definition.
(I've seen this before)
'carriage they say' is the wordplay.
'carriage' becomes 'gait' (I've seen this before).
'they say' shows a homophone (sound like).
'gait' is a homophone of 'GATE'.
'for' acts as a link.
(Other definitions for gate that I've seen before include "Means of entry" , "Movable barrier in a fence or wall" , "Portal" , "Barrier - door" , "Movable opening" .)