Spot something in the jeweller's window (9)
I believe the answer is:
carbuncle
'spot' is the definition.
'something in the jeweller's window' is the wordplay.
I cannot really understand how this works, but
'window' could be 'car' (car window is a kind of window) and 'car' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for carbuncle that I've seen before include "Architectural eyesore" , "Large boil-like inflammation - gemstone" , "Sort of boil; a gem" , "growth" , "stone" .)