ἢ λέγε τι σιγῆς κρεῖττον ἢ σιγὴν ἔχε → either say something better than silence or keep silence (Menander)
Use adj., Ar. and P. δικανικός.
advocate: P. and V. συνήγορος, ὁ, or ἡ, σύνδικος, ὁ, or ἡ, P. παράκλητος, ὁ.