Lip is part of one's face (5)
I believe the answer is:
cheek
I believe this is a quadruple definition!!
'lip' is the first definition.
(I've seen this before)
'is' acts as a link.
'part' is the second definition.
(cheek is a kind of part)
'of' is a link.
'one's' is the third definition.
Both the definition and answer are adjectives. Maybe you can see a link between them that I can't see?
'face' is the fourth definition.
(I know that face can be written as cheek)
Can you help me to learn more?
(Other definitions for cheek that I've seen before include "Chap" , "Nerve - part of the face" , "lip, or nearby part of head" , "Effrontery" , "Informal impertinence from side of face" .)