Foul and sticky leaving South Carolina for Channel Isles (7)

I believe the answer is:

vicious

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'foul' is the definition.
(thesaurus)

I don't understand how the rest of the clue works.

(Other definitions for vicious that I've seen before include "Malicious, brutal" , "Deliberately nasty" , "Brutal, savage and dangerous" , "Cruel, wicked" , "Malicious - degenerate" .)

I've seen this clue in The Guardian.

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