Decorate, festoon (5)
I believe the answer is:
adorn
I believe this clue is a double definition.
'decorate' is the first definition.
(synonyms)
'festoon' is the second definition.
(I've seen this in another clue)
(Other definitions for adorn that I've seen before include "Festoon" , "Make more attractive" , "Improve appearance" , "Deck" , "get dressed!" .)