Though indispensable, such a man must have the correct cards (5-4)
I believe the answer is:
right-hand
'though indispensable such a man must have' is the definition.
I can't tell whether this defines the answer.
'correct cards' is the wordplay.
'correct' becomes 'right' (right can mean correct).
'cards' becomes 'hand' (I've seen this in other clues).
'right'+'hand'='RIGHT-HAND'
'the' is the link.
Can you help me to learn more?
(Other definitions for right-hand that I've seen before include "drive in a British vehicle" , "Principally relied on such" .)