Clear quartz (7)
I believe the answer is:
crystal
'clear quartz' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for crystal that I've seen before include "Globe for the fortune-teller" , "Type of clear-cut, lucent glass" , "The fortune teller may use a . . . . . . . ball" , "Quality glass" , "Quartz, for example" .)