For the road, it may well be unwise (3)
I believe the answer is:
one
'unwise' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'for the road it may well' is the wordplay.
I cannot quite see how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found in the answer.
The remaining letters 'on' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'be' is the link.
Can you help me to learn more?
(Other definitions for one that I've seen before include "both halves" , "Leading cardinal" , "1" , "Single and undivided" , "Ace" .)