Dangerous woman, but she will give warning (5)
I believe the answer is:
siren
'warning' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for siren that I've seen before include "Dangerously fascinating woman" , "Loud whistle for sea temptress" , "Nymph supposed to have lured sailors to destruction on rocks" , "Rinse (anag) - sea nymph" , "Loud whistle or sea witch" .)