Crowd packing terracing at Edgbaston (4)
I believe the answer is:
gate
'crowd' is the definition.
(gate can refer to the crowd for a sporting event)
'packing terracing at edgbaston' is the wordplay.
'packing' says the answer is hidden in the clue.
'GATE' is hidden within 'terracing at edgbaston'.
(Other definitions for gate that I've seen before include "Barrier - door" , "Entry barrier as to field" , "Hinged barrier in an entrance" , "Punish student" , "Confine to college" .)