Town crier's shout (4)
I believe the answer is:
oyez
'town crier's shout' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for oyez that I've seen before include "Town crier's call (Z, not S)" , "Hear this" , "Pay attention" , "Cry of the old town crier" , "Town crier's 'Attention!'" .)