A firm "Stop" (7)

I believe the answer is:

staunch

I believe this is a double definition.

'a firm' is the first definition.
(I've seen this in another clue)

'stop' is the second definition.
(I know that staunch is a more specific form of the action check)

(Other definitions for staunch that I've seen before include "Very loyal; stop (a flow of blood)" , "Sturdy" , "Very loyal, committed" , "making it watertight" , "Check" .)

I've seen this clue in the Evening Standard.

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