15a) Aims the weapon and brings the building to the ground (6) ???E?S
6 & 2d) The siege of Troy, for instance, producing protracted interest! (4-4, 10) ?O?G-?E?M, I??E?T????
18d) Head of the church in fixed group of worshippers (4) ??C?
20d) The French country settles an account (4) P?Y?