On the road, perhaps, change gear (4)
I believe the answer is:
rage
'on the road' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'change gear' is the wordplay.
'change' is an anagram indicator.
'gear' with letters rearranged gives 'RAGE'.
'perhaps' is the link.
Can you help me to learn more?
(Other definitions for rage that I've seen before include "Uncontrollable anger" , "Uncontrolled anger" , "Frenzy" , "a poetic response to dying light?" , "Mania" .)