She has grey matter - beauty, too (5)
I believe the answer is:
pearl
'she' is the definition.
'grey matter beauty too' is the wordplay.
I cannot quite understand how this works, but
'matter' could be 'pear' (pear is a kind of matter) and 'pear' is present in the answer.
A single letter 'l' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'has' is the link.
Can you help me to learn more?
(Other definitions for pearl that I've seen before include "Lustrous globule prized as a gem" , "Gem from oyster" , "something highly valued" , "Smooth lustrous round structure of calcium carbonate" , "Girl < , pretty" .)