Cheek, or another part of face (3)
I believe the answer is:
lip
This clue might be a double definition.
'cheek' is the first definition.
(both can mean insolence or rudeness)
'another part of face' is the second definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'or' is the link.
Can you help me to learn more?
(Other definitions for lip that I've seen before include "Sauce" , "Part of mouth or cheek" , "Impudent talk from part of the face" , "giving such insincere service" , "Top edge of a vessel" .)