Dodgy, being at the mercy of cards one’s dealt (9)
I believe the answer is:
underhand
'dodgy' is the definition.
'at the mercy of cards one's dealt' is the wordplay.
'at the mercy of' becomes 'under'.
'cards one's dealt' becomes 'hand'.
'under'+'hand'='UNDERHAND'
'being' acts as a link.
(Other definitions for underhand that I've seen before include "In a secret or dishonest way" , "Displaying craft" , "Done dishonestly" , "Deceptively" , "Sneaky" .)