Tooth point (4)
I believe the answer is:
cusp
'tooth point' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cusp that I've seen before include "Pointed end (e.g. on tooth)" , "Pointed meeting of curves" , "Horn of moon" , "Turning point on which important developments depend" , "Pointed end where two curves meet" .)