They tread on the road! (5)
I believe the answer is:
tyres
'they' is the definition.
Both the definition and answer are plural nouns.
Maybe they are linked in a way I don't understand?
'tread on the road' is the wordplay.
I cannot really understand how this works, but
'on' could be 're' (regarding) and 're' is found within the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
This explanation may well be incorrect...
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" .)