Want to hold stone? That's settled (6)
I believe the answer is:
nested
'settled' is the definition.
(I've seen this in another clue)
'want to hold stone?' is the wordplay.
'want' becomes 'need' (needing is a kind of wanting).
'to hold' is an insertion indicator.
'stone?' becomes 'st'.
'need' enclosing 'st' is 'NESTED'.
'that's' acts as a link.
(Other definitions for nested that I've seen before include "Settled in comfortably, snuggled up" , "Built a home" , "Settle in comfortably like a bird" , "Settled in comfortably like bird" , "Of bird, settled in to home" .)