Heartless boatswain Channel port legally constrained (5,4)

I believe the answer is:

bound over

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'legally constrained' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'heartless boatswain channel port' is the wordplay.
'heartless' means to remove the middle letters.
'boatswain' becomes 'bosun' ('bosun' can be a synonym of 'boatswain').
'channel port' becomes 'dover' (English Channel port).
'bosun' with its centre taken out is 'boun'.
'boun'+'dover'='BOUND OVER'

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(Other definitions for bound over that I've seen before include "Clear" , "Legally under restraint - jump across" , "Placed under a (specified) legal obligation" , "Put under a legal obligation" , "subject to legal constraint" .)

I've seen this clue in The Telegraph.

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