Glasses with bits of dust detected (5)
I believe the answer is:
specs
'glasses' is the definition.
(spectacles)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for specs that I've seen before include "Glasses (abbr)" , "Glasses (sl.)" , "shades?" , "Glasses (informal)" , "Detailed plan" .)