Embellishment of December speech (10)
I believe the answer is:
decoration
'embellishment' is the definition.
(thesaurus)
'december speech' is the wordplay.
'december' becomes 'Dec' (synonyms).
'speech' becomes 'oration' (oration is a kind of speech).
'dec'+'oration'='DECORATION'
'of' is the link.
(Other definitions for decoration that I've seen before include "award" , "Adornment - medal" , "Ornaments - medal" , "New Year's honour, say" , "Medal; ornament" .)