Saw car encased in lead (7)
I believe the answer is:
proverb
'saw' is the definition.
(a saw can mean a proverb or maxim)
'car encased in lead' is the wordplay.
I cannot quite understand how this works, but
'car' could be 'rover' (former British car manufacturer) and 'rover' is found within the answer.
'lead' could be 'pb' (Pb is the chemical symbol for lead) and 'pb' is present in the leftover letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for proverb that I've seen before include "Familiar saying" , "Make haste slowly, perhaps" , "Short saying expressing a supposed truth" , "Wise saying" , "Maxim" .)