Pledge that may be taken on board (4)

I believe the answer is:

pawn

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'pledge' is the definition.
(I know that pawn is a type of pledge)

I don't understand how the rest of the clue works.

(Other definitions for pawn that I've seen before include "Deposit as security for a loan" , "piece on board" , "The foot-soldier in chess" , "Chessman often sacrificed" , "Chesspiece" .)

I've seen this clue in The Globe and Mail.

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