Crossword Genius

Run to eccentric payment method (6,4)

Ross

I believe the answer is:

charge card

I'm a little stuck... Click here to teach me more about this clue!

'payment method' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'run to eccentric' is the wordplay.
'run' becomes 'charge'.
'to eccentric' becomes 'card' (I've seen this before).
'charge'+'card'='CHARGE-CARD'

Can you help me to learn more?

(Other definitions for charge card that I've seen before include "shopping assistant" , "Means of buying goods" .)

I've seen this clue in The Daily Express.
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