Spring's shape (4)
I believe the answer is:
coil
'spring's shape' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for coil that I've seen before include "Series of concentric circles" , "Wound length (of rope)" , "Wind (wire, rope, etc)" , "Curl, loop" , "Convolute" .)