SOLUTION 677:

ACROSS 6 IceAge, 7 Cherub, 10 Hanover, 11 Roget, 12 Ludo, 13 Divot, 16 Frost,

17 Hero, 20 El Cid, 21 At birth, 22 Oolong, 23 Weasel.

DOWN 1 Michelangelo, 2 Kennedy, 3 Agave, 4 Cheroot, 5 Frigg, 8 Bat Out of Hell,

9 Artie Shaw, 14 Trident, 15 Leprosy, 18 Scale, 19 Ibsen.