Jeweler's eyepiece (5)
I believe the answer is:
loupe
'jeweler's eyepiece' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for loupe that I've seen before include "Jeweller's magnifying glass" , "Jeweller's eyeglass" , "instrument in view of fine work" , "Jeweller's eyepiece" .)