Wood spirit is something used to promote Prohibition? (5)
I believe the answer is:
dryad
'wood spirit' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for dryad that I've seen before include "Mythological wood nymph" , "Nymph of trees" , "Wood-nymph" , "Woodland nymph" , "Woodland deity" .)