WORLD'S SMALLEST HARDEST

▶ Across 1. Desirous for (4)

4. (Chem symbol) rubidium (2) 5. Symbol for micron (2) 6. Religious faction (4)

▶ Down 1. Jacket parts (4)

2. Part of speech (abbr) (2) 3. Extinguish (4)

5. US senator (abbr) (2)