### Clue: Jasper, perhaps a jester (10)
### Answer: TOUCHSTONE 
 ### Explanation: Definition: Jasper,perhaps a jester
 Double defn: 1. A piece of the mineral, jasper, used to test and identify precious metal alloys; and 2nd: A name, an example of which/perhaps, is that of the court jester in Shakespeare's play, As You Like It.