Get a poor number of spectators (4)
I believe the answer is:
gate
'number of spectators' is the definition.
(number of people attending a sports event)
'get a poor' is the wordplay.
'poor' indicates an anagram.
'get'+'a'='geta'
'geta' anagrammed gives 'GATE'.
(Other definitions for gate that I've seen before include "Plane-boarding point" , "Hinged barrier in an entrance" , "Opening in a wall or fence" , "Attendance figure" , "Entrance to a Dublin theatre" .)