Viewing aid picked up the smallest things (6)
I believe the answer is:
specks
'smallest things' is the definition.
(specks are small particles)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for specks that I've seen before include "Small marks" , "Tiny pieces as of dust" , "Small particles or spots" , "What may help one to see" , "Small pieces as of dust" .)