Win audience with small number that we hear might be Grecian (4)
'win audience with small number that' is the definition.
'earn' can be an answer for 'win' (I've seen this before). I am not sure about the remainder of the definition.
'we hear might be grecian' is the wordplay.
'we hear' shows a homophone (sound like).
'might be grecian' becomes 'urn' (as in Keats' Ode on a Grecian Urn).
'urn' is a homophone of 'EARN'.
(Other definitions for earn that I've seen before include "Gain (money, reputation, etc)", "Take home", "net", "Get by working", "Win".)