Vehicle family member used to carry black gemstone (9)
I believe the answer is:
carbuncle
'gemstone' is the definition.
(I know that carbuncle is a type of garnet)
'vehicle family member used to carry black' is the wordplay.
I cannot really see how this works, but
'vehicle' could be 'car' (car is a kind of vehicle) and 'car' is located in the answer.
'black' could be 'b' (abbreviation as in pencil classifications) and 'b' is located in the answer.
'family member' could be 'uncle' (brother of a parent) and 'uncle' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for carbuncle that I've seen before include "Skin eruption - gemstone" , "National Gallery's Sainsbury Wing?" , "Red gemstone; sort of boil" , "Sort of boil; a gem" , "Bright red gem; boil" .)