Arctic whale (7)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">arctic whale</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for narwhal that I've seen before include "Small Arctic whale" , "Warn Hal there's a whale here" , "Small tusked whale" , "Marine mammal, the male having a spiral ivory tusk" , "beast" .)
(Another definition for bowhead that I've seen is " protected swimmer".)