Decorate, so often badly (7)
I believe the answer is:
festoon
'decorate' is the definition.
(festooning is a kind of decorating)
'so often badly' is the wordplay.
'badly' indicates an anagram.
'so'+'often'='sooften'
'sooften' anagrammed gives 'FESTOON'.
(Other definitions for festoon that I've seen before include "Decorative chain" , "Ornamental garland" , "So often (anag.)" , "Hung garland" , "Adorn (with garlands?)" .)