Leading man needs blood — gallons (4)

I believe the answer is:

king

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'leading man' is the definition.
'king' can be an answer for 'man' (man can mean a chess piece). I am unsure of the 'leading' bit.

'blood gallons' is the wordplay.
'blood' becomes 'kin' (both can mean one's family).
'gallons' becomes 'G' (abbreviation).
'kin'+'g'='KING'

'needs' acts as a link.

Can you help me to learn more?

(Other definitions for king that I've seen before include "Playing-card" , "Most important chessman" , "See 22" , "VIP" , "Chesspiece which mustn't be lost" .)

I've seen this clue in The Independent.

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