Tap thigh-bone endlessly in jittery manner at get together (4,2)

I believe the answer is:

team up

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'get together' is the definition.
(I've seen this in another clue)

I don't understand the remainder of the clue.

(Other definitions for team up that I've seen before include "Unite for a common goal" , "Couple" , "Join" , "Brighton and Hove Albion following promotion?" .)

I've seen this clue in The Irish Times.

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