Ringword puzzle #65 - clues

1: Flashlight, to the British
4: Drink without stopping, rhythmically
7: Blockaded Strip in Palestine
9: Koan meditation or shikantaza
12: Snake's sin, opposed to kindness
15: Leavening fungus
17: Prefix for -nomy, -logy, and -naut
21: Prefix for -pus, -thorpe, and -ber