Pure underwear, half with skirts off (6)
I believe the answer is:
vestal
'pure' is the definition.
(I know that pure can be written as vestal)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for vestal that I've seen before include "Modest female" , "Like virgins of old" , "Woman dedicated to celibacy" , "Valets for old Roman virgin" , "Virgin charged with keeping alight the fire on the altar to a Roman goddess" .)