Garland often so properly arranged (7)
I believe the answer is:
festoon
'garland' is the definition.
(I've seen this before)
'often so properly arranged' is the wordplay.
'properly arranged' is an anagram indicator (I've seen this in other clues).
'often'+'so'='oftenso'
'oftenso' anagrammed gives 'FESTOON'.
(Other definitions for festoon that I've seen before include "Ornamental garland" , "Decorate with hanging ornaments" , "Hung garland" , "Decoration" , "Ornamental chain/garland" .)