Son taken in by detailed scam on board ship -- alternatively, one might put the squeeze on you? (3,11)

I believe the answer is:

boa constrictor

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But I can't explain it at all! Could you help me understand?

(Other definitions for boa constrictor that I've seen before include "Medium-sweet sherry" , "Large snake" .)

I've seen this clue in The Telegraph.

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