Highly-prized possession (8)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
treasure
'highly-prized possession' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for treasure that I've seen before include "Valued friend" , "... Island (R.L.Stevenson)" , "much-loved person" , "Set great store by" , "Value highly" .)