Spiraled (7)
(Other definitions for helical that I've seen before include "Curled like corkscrew" , "Spiral-shaped" , "In the form of a spiral" , "Like the pattern on a snail's shell" , "Like a spiral or spring" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">spiraled</span>' is the definition.<br/ ><span class="explanation-format__explanation">('corkscrew' can be a synonym of 'spiral')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Another definition for corkscrewed that I've seen is " Bottle stoppers may have been this".)