Wedding attendant married on fateful day in interwoven fabric (10)
I believe the answer is:
bridesmaid
'wedding attendant' is the definition.
(I've seen this before)
'married on fateful day in interwoven fabric' is the wordplay.
'married' becomes 'm' (abbreviation, e.g. in genealogy).
'on' means one lot of letters go next to another.
'fateful day' becomes 'ides' (Julius Caesar was killed on the ides of March).
'in' is an insertion indicator.
'interwoven fabric' becomes 'braid' (fabric interweaving multiple strands).
'm' put after 'ides' is 'idesm'.
'idesm' going inside 'braid' is 'BRIDESMAID'.
(Other definitions for bridesmaid that I've seen before include "match participant" , "Attendant at wedding" , "one's holding up train perhaps" .)