Sinbad's giant bird (3)
I believe the answer is:
roc
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sinbad's giant bird</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for roc that I've seen before include "Mythical bird; sounds like boulder" , "Enormous legendary bird" , "Legendary flier" , "Vast legendary bird" , "Bird imagined" .)