Returning knight stashes ring while breaching border in an act of bravery (7)

I believe the answer is:

heroism

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'bravery' is the definition.
(heroism is brave behaviour)

I don't understand the remainder of the clue.

(Other definitions for heroism that I've seen before include "brave action" , "Courageous quality" , "Outstanding courage" , "Very brave conduct or act of valour" , "Act of unselfish bravery" .)

I've seen this clue in The Irish Times.

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