The type of Mole that leaves a mark reversing vehicle - it's not very nice scratching the side (6)
I believe the answer is:
naevus
'the type of mole that leaves a mark reversing vehicle it's not very nice scratching the side' is the definition.
The definition suggests a singular noun which matches the answer.
This is all the clue.
Can you help me to learn more?
(Other definitions for naevus that I've seen before include "Birthmark or mole" , "A scarlet birthmark on skin" , "A red-coloured birthmark" , "disfiguring mark" , "A red birthmark on skin" .)