Some wonderful marine bird (6)
I believe the answer is:
fulmar
'bird' is the definition.
(fulmar is a kind of bird)
'some wonderful marine' is the wordplay.
'some' indicates the answer is hidden within the clue (some parts of the word are used).
'FULMAR' is hidden in the letters of 'wonderful marine'.
(Other definitions for fulmar that I've seen before include "Heavy short-tailed oceanic bird" , "Gull-like sea bird" , "Heavy short-tailed polar bird" , "Get an strange armful of this seabird" , "Bird of petrel family" .)