Bird in a cove fluttering close to boat (6)
I believe the answer is:
avocet
'bird' is the definition.
(avocet is a kind of bird)
'a cove fluttering close to boat' is the wordplay.
'fluttering' indicates an anagram.
'close to' suggests the final letters (the close/ending of).
The final letter of 'boat' is 't'.
'cove' anagrammed gives 'voce'.
'a'+'voce'+'t'='AVOCET'
'in' acts as a link.
(Other definitions for avocet that I've seen before include "Long-legged wading bird with upward-curving bill" , "Shorebird - octave (anag)" , "Long-legged shorebird with upward-curving bill" , "Flier" , "Wading bird with upturned bill" .)