Sew decorations on bride more extravagantly (9)
I believe the answer is:
embroider
'sew decorations' is the definition.
(I know this)
'on bride more extravagantly' is the wordplay.
'on' means one lot of letters go next to another.
'extravagantly' indicates an anagram (an unusual or extravagant version of the letters).
'bride' put after 'more' is 'morebride'.
'morebride' is an anagram of 'EMBROIDER'.
(Other definitions for embroider that I've seen before include "Do decorative needlework" , "Exaggerate" , "Dress up" , "Elaborately sew" , "Sew decoration onto" .)