In the shape of a helix (6)
I believe the answer is:
spiral
'in the shape of a helix' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for spiral that I've seen before include "Sir, pal inds in continuous loops" , "Corkscrew curve" , "Shape of coil or helix" , "Ever widening curve" , "In flight manoeuvre" .)