Nautical steering device (6)
I believe the answer is:
rudder
'nautical steering device' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rudder that I've seen before include "It is used to steer boat or plane" , "It guides" , "Ship's steerer" , "Boat's steering device" , "Helm" .)