Noble’s headgear, gold one used within court (7)
I believe the answer is:
coronet
'noble's headgear' is the definition.
'coronet' can be an answer for 'headgear' (coronet is a kind of headgear). I am not certain of the 'noble's' bit.
'gold one used within court' is the wordplay.
I cannot really see how this works, but
'gold' could be 'or' ('or' is the heraldic name for gold) and 'or' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for coronet that I've seen before include "Small crown" , "Simple crown" , "Circular floral head decoration" , "Diadem" , "sign of rank" .)