Temptresses: they warn us! (6)
I believe the answer is:
sirens
'temptresses' is the definition.
('siren' can be a synonym of 'temptress')
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for sirens that I've seen before include "Sea nymphs" , "Loud wailing warnings sounds" , "Alarm whistles or temptresses of sailors" , "They lured mariners on to rocks with loud whistles?" , "Loud warning signals" .)