Don, for example – lead-free motorist (5)
I believe the answer is:
river
'don for example' is the definition.
(don is a kind of river)
'lead-free motorist' is the wordplay.
'lead-free' means to remove the first letter (the letter which leads the word is removed).
'motorist' becomes 'driver' (I've seen this before).
'driver' with its initial letter removed is 'RIVER'.
(Other definitions for river that I've seen before include "Thames is one" , "Large flow of liquid" , "Current" , "One splits" , "Eg, the Rhine" .)