A black suit is useful kit for a burial (6)
I believe the answer is:
spades
I believe this is a double definition.
'a black suit' is the first definition.
(I've seen this before)
'useful kit for a burial' is the second definition.
(a spade might be used to dig a grave)
'is' is the link.
(Other definitions for spades that I've seen before include "trumps sometimes" , "Suit in pack of cards" , "Black suit" , "Digging implements" , "Digging tools and card suit" .)