Crossword Genius

Out of danger, if the telephone is incapable of receiving calls (3,3,4)

Ross

I believe the answer is:

off the hook

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'out' is the definition.
Both the answer and definition are adjectives. Perhaps there's a link between them I don't understand?

I don't understand the rest of the clue.

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(Other definitions for off the hook that I've seen before include "Exculpated" , "Out of danger - freed of guilt" , "Close to the Dutch shore" , "Safe from further blame or obligation" , "near to Holland landmark?" .)

I've seen this clue in the Evening Standard.
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