Spread or widened out (9)
I believe the answer is:
eiderdown
'spread' is the definition.
(thesaurus)
'or widened out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'or'+'widened'='orwidened'
'orwidened' is an anagram of 'EIDERDOWN'.
(Other definitions for eiderdown that I've seen before include "What might keep one warm" , "Warm bedcover" , "I wondered about this warm bed covering" , "Find cover" , "thermal insulation" .)