She has a certain lustre (5)
I believe the answer is:
pearl
'she' is the definition.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for pearl that I've seen before include "Oyster growth" , "one regularly in stitches" , "Smooth lustrous round structure of calcium carbonate" , "Highly-valued thing" , "Precious stone from shellfish" .)