Yank to succeed in forming relationship? (4)

I believe the answer is:

pull

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'yank' is the definition.
(I know that yank is a more specific form of pull)

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for pull that I've seen before include "Tell that to the marines" , "withdraw" , "Heave" , "Tug - influence" , "Draw towards oneself" .)

I've seen this clue in The Times.

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