Top of skirt has new waistband (4)
I believe the answer is:
sash
'waistband' is the definition.
(synonyms)
'top of skirt has new' is the wordplay.
'top of' says to take the initial letters.
'new' indicates an anagram.
The initial letter of 'skirt' is 's'.
'has' is an anagram of 'ash'.
's'+'ash'='SASH'
(Other definitions for sash that I've seen before include "Cummerbund" , "Ribbon as a symbol of rank" , "Window frame - shoulder band" , "Girdle" , "Broad band, the one me father wore?" .)