They tread on the road! (5)
I believe the answer is:
tyres
'they' is the definition.
Both the answer and definition are plural nouns.
Perhaps they are linked in a way I don't understand?
'tread on the road' is the wordplay.
I cannot really see how this works, but
'on' could be 're' (regarding) and 're' is found in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tyres that I've seen before include "Rubber wheel covers" , "Wheel coverings" , "Wheel hoops" , "rubber rings" .)