Our one quest, oddly, finding semiprecious stone (9)
I believe the answer is:
turquoise
'semiprecious stone' is the definition.
(turquoise is a semi-precious stone)
'our one quest oddly' is the wordplay.
'one' becomes 'I' (Roman numeral).
'oddly' indicates anagramming the letters.
'our'+'i'+'quest'='ouriquest'
'ouriquest' anagrammed gives 'TURQUOISE'.
'finding' is the link.
(Other definitions for turquoise that I've seen before include "Aquamarine colour" , "Shade of blue - gemstone" , "Greenish-blue gem" , "Birthstone for December" , "not quite green" .)