Last three. 20a Fatal tipple for the "false, fleeting and perjur'd" (8) - - - V - S - A Can only think of MALVASIA, but can't see the connection.
17d Frame traitor (7) - - - E - E - T Second letter 'A' if MALVASIA is right.
24a Bill known to be associated with Galatea (4) A - I -
Thanks.