Rinses out warning devices (6)
I believe the answer is:
sirens
'warning devices' is the definition.
(I've seen this in another clue)
'rinses out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'rinses' is an anagram of 'SIRENS'.
(Other definitions for sirens that I've seen before include "Alarm whistles or temptresses of sailors" , "Warning devices with loud wailing noise" , "Loud warning signals" , "Loud wailing warnings sounds" , "Sea nymphs" .)