Some Icelandic creature (5)
I believe the answer is:
eland
'creature' is the definition.
(eland is a type of antelope)
'some icelandic' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'ELAND' is hidden within 'icelandic'.
(Other definitions for eland that I've seen before include "Large spiral-horned African antelope" , "Browser" , "Largest living antelope" , "Led an (anag) -- antelope" , "One browses in the African plain" .)