Scratching nail into neck (8)
I believe the answer is:
scraping
'scratching' is the definition.
(I know that scratching can be written as scraping)
'nail into neck' is the wordplay.
'nail' becomes 'pin' (both can mean a sharp object).
'into' indicates putting letters inside.
'neck' becomes 'scrag' (I've seen this in another clue).
'pin' put into 'scrag' is 'SCRAPING'.
(Other definitions for scraping that I've seen before include "Grating" , "Bowing and ..., kowtowing" .)