Some gent ordered a jewel (8)
I believe the answer is:
gemstone
'a jewel' is the definition.
(I've seen this before)
'some gent ordered' is the wordplay.
'ordered' indicates an anagram.
'some'+'gent'='somegent'
'somegent' is an anagram of 'GEMSTONE'.
(Other definitions for gemstone that I've seen before include "Eg, diamond or ruby" , "It's considered precious" , "Physical power" , "Eg, sapphire" , "[RUBY] , for example" .)