Precious stone in crown of Azerbaijan (5)
I believe the answer is:
topaz
'precious stone' is the definition.
(I've seen this before)
'crown of azerbaijan' is the wordplay.
'crown' becomes 'top' (synonyms).
'of azerbaijan' becomes 'az' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'top'+'az'='TOPAZ'
'in' is the link.
Can you help me to learn more?
(Other definitions for topaz that I've seen before include "Type of gemstone" , "Yellow quartz used for gemstones" , "Precious stone - dark yellow colour" , "Shade of yellow -- gem" , "valuable item" .)