Unlike a cameo, it has a certain hollow beauty (8)
I believe the answer is:
intaglio
'beauty' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for intaglio that I've seen before include "carved design" , "favoured artist's technique" , "Gemstone with a design engraved in its surface" , "Engraving cut into a hard surface" , "Seal with a sunken design" .)