Black suit used in the digs (6)
I believe the answer is:
spades
'digs' is the definition.
(spading is a kind of digging)
'black suit used in' is the wordplay.
'black suit' becomes 'spade' (I've seen this in another clue).
'used in' becomes 's' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'spade'+'s'='SPADES'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for spades that I've seen before include "Suit in pack of cards" , "Card suits and shovels" , "Black suit" , "those getting soiled?" , "trumps sometimes" .)