Lone broadcast at Christmas (4)
I believe the answer is:
noel
'christmas' is the definition.
(synonyms)
'lone broadcast' is the wordplay.
'broadcast' indicates an anagram (letters scattered or cast around).
'lone' is an anagram of 'NOEL'.
'at' is the link.
(Other definitions for noel that I've seen before include "Festivity" , "Festive season" , "- - Coward, playwright" , "Christmas carol" , "Season around the 25th December" .)