Listen out for decoration (6)
I believe the answer is:
tinsel
'for decoration' is the definition.
(I have seen 'Showy decoration' mean 'tinsel' so perhaps 'decoration' could also mean 'tinsel')
'listen out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'listen' anagrammed gives 'TINSEL'.
(Other definitions for tinsel that I've seen before include "Showy decoration" , "Inexpensive sparkly stuff" , "Shiny stuff of silent kind" , "Glittering Christmas strip" , "Glittering threads for decoration" .)