Plane stunt (4)
I believe the answer is:
loop
'plane stunt' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for loop that I've seen before include "Computer subroutine" , "Curve that bends round and crosses itself" , "Noose" , "Oval or U-shaped coil or bend" , "Shape formed by a closed curve that does not intersect itself" .)