Reference point, touchstone (8)
I believe the answer is:
standard
This clue is a double definition.
'reference point' is the first definition.
(standard is a kind of reference point)
'touchstone' is the second definition.
(I know that touchstone can be written as standard)
(Other definitions for standard that I've seen before include "Degree of quality" , "type of flag" , "Basic criterion" , "Reference point against which other things can be evaluated" , "authority" .)