Penitential attire (9)
I believe the answer is:
sackcloth
'penitential attire' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sackcloth that I've seen before include "With ashes, it's a sign of repentance" , "part of repentance" , "In which penitent is" , "Penitent's attire" , "rough stuff" .)