Second person getting some teeth out (4)
I believe the answer is:
thou
'second person' is the definition.
(historical second person pronoun)
'some teeth out' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'THOU' can be found hidden inside 'teeth out'.
'getting' acts as a link.
(Other definitions for thou that I've seen before include "You (formerly)" , "1,000 (abbr)" , "You, poetically of old" , "Prominent pronoun of the King James Bible; the modern-day 'you'" , "Biblical 'you'" .)