See dry rot, unfortunately in naval vessel (9)
I believe the answer is:
destroyer
'naval vessel' is the definition.
(I've seen this before)
'see dry rot unfortunately' is the wordplay.
'unfortunately' is an anagram indicator.
'see'+'dry'+'rot'='seedryrot'
'seedryrot' with letters rearranged gives 'DESTROYER'.
'in' is the link.
(Other definitions for destroyer that I've seen before include "Large warship" , "Vandal" , "Red oyster (anag)" , "Wrecker" , "Siva?" .)