She's a beauty, but not without grey matter (5)
I believe the answer is:
pearl
'grey matter' is the definition.
'pearl' can be an answer for 'grey' (thesaurus). I'm not certain of the 'matter' bit.
'she's a beauty but not without' is the wordplay.
I cannot really see how this works, but
'a' is found in the answer.
'she' could be 'perl' and 'perl' is found within the remaining letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for pearl that I've seen before include "Drop" , "Gem from oyster" , "one regularly in stitches" , "Gem from the sea" , "Oyster's gem" .)