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 anagramming the letters (out can mean wrong or inaccurate).
'listen' is an anagram of '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" .)