Fold your attire finally into case (6)
I believe the answer is:
crease
'fold' is the definition.
('crease' can be a synonym of 'fold')
'your attire finally into case' is the wordplay.
'finally' suggests the final letters.
'into' indicates putting letters inside.
The last letters of 'your attire' are 're'.
're' going into 'case' is 'CREASE'.
(Other definitions for crease that I've seen before include "Cricket line; wrinkle" , "batsman reaching it" , "Wrinkle on the cricket pitch?" , "Furrow, wrinkle" , "Mark made by fold" .)