Rinse out a warning device (5)
I believe the answer is:
siren
'a warning device' is the definition.
(I've seen this in another clue)
'rinse out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'rinse' is an anagram of 'SIREN'.
(Other definitions for siren that I've seen before include "Warning device - femme fatale" , "Vamp; alarm" , "Device making a loud wailing sound" , "Alluring female" , "Alarm; temptress" .)