Lip, brink (4)
I believe the answer is:
brim
This clue is a double definition.
'lip' is the first definition.
(I know that lip can be written as brim)
'brink' is the second definition.
(I've seen this in another clue)
(Other definitions for brim that I've seen before include "Lip of bowl, cup etc" , "Edge (of cup or hat)" , "Edge or rim" , "Circumference" , "Lip of a vessel" .)