Docked in unusually still sea (8)
I believe the answer is:
tailless
'docked in' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?
'unusually still sea' is the wordplay.
'unusually' is an anagram indicator.
'still'+'sea'='stillsea'
'stillsea' anagrammed gives 'TAILLESS'.
Can you help me to learn more?
(Other definitions for tailless that I've seen before include "Physical characteristic of Manx cat" , "Like frogs and toads, say" , "Physical condition of Manx cat" .)