Ground grippers (6)
I believe the answer is:
cleats
'ground grippers' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cleats that I've seen before include "On which to fasten ropes on board" , "Footwear stabilisers found in castle" , "Devices on board ship for fastening ropes" , "Projections around which ropes are secured" , "Projections around which a rope can be tied" .)