Fish from quiet boat (5)
I believe the answer is:
shark
'fish' is the definition.
(shark is a kind of fish)
'quiet boat' is the wordplay.
'quiet' becomes 'sh'.
'boat' becomes 'ark' (ark is a kind of boat).
'sh'+'ark'='SHARK'
'from' is the link.
(Other definitions for shark that I've seen before include "Unscrupulous greedy person" , "Predatory creature" , "Predatory fish (or person?)" , "eg Jaws" , "danger at sea" .)