She's like stone to a soft-headed aristocrat (5)
I believe the answer is:
pearl
'she's' is the definition.
'soft-headed aristocrat' is the wordplay.
'soft' becomes 'pp' (musical abbreviation for pianissimo).
'headed' means to remove the first letter (head can mean to remove the top from something).
'aristocrat' becomes 'Earl' (earl is a kind of aristocrat).
'pp' with its initial letter taken away is 'p'.
'p'+'earl'='PEARL'
'like stone to a' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for pearl that I've seen before include "Off-white colour" , "Gem; an attacked Harbor" , "Precious jewel from the oyster" , "Oyster growth" , "Lustrous structure inside an oyster-shell" .)