Type of mineral set in priory ordered (4,7)
I believe the answer is:
iron pyrites
'type of mineral' is the definition.
(I've seen this before)
'set in priory ordered' is the wordplay.
'ordered' indicates anagramming the letters.
'set'+'in'+'priory'='setinpriory'
'setinpriory' anagrammed gives 'IRON PYRITES'.
(Other definitions for iron pyrites that I've seen before include "Type of mineral" , "Fool's gold" .)