Cycling without restriction rocks? (4)
I believe the answer is:
reef
'rocks?' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for reef that I've seen before include "Atoll protector" , "Low-lying coral ridge" , "Rocks in shallow water - kind of knot" , "Ridge of rock or sand just below sea surface" , "Ridge of rock underwater" .)