Cry of an old town crier (4)
I believe the answer is:
oyez
'cry of an old town crier' 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)" , "Town crier's shout" , "Call of hte old Town Crier" , "Cry of the old town crier" , "Call of public crier" .)