Thousands on the run to get highest bid (5,4)

I believe the answer is:

grand slam

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But I can't explain it at all! Could you help me understand?

(Other definitions for grand slam that I've seen before include "Winning all the tricks or matches" , "Winning of all tricks (or major tournaments)" , "sporting triumph" , "Winning all bridge tricks, or rugby games" , "It's extremely tricky" .)

I've seen this clue in The Hindu.

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