21 LUST - powerful drive, RUM - spirit. It refers to a period of 5 years, so 20 (19 more) needed for a century
28 D - fourth rate (after A, B, C), RAM -stuff (as in packing), HOP - bound. I haven't heard the term, but presumably it's a US bar
17 CARE - trouble, SIRE - father, reversed, T(ime)