Frank's refusal to bring down leader (4)

I believe the answer is:

open

'frank's' is the definition.
(synonyms)

I cannot understand how the remainder of the clue works.

(Other definitions for open that I've seen before include "Not shut or secret" , "Overt" , "Allowing entry and exit" , "Plain" , "simple" .)

I've seen this clue in The Guardian.

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