Plans of small particles broadcast (5)
I believe the answer is:
specs
'plans' is the definition.
(specifications)
'small particles broadcast' is the wordplay.
'small particles' becomes 'specks'.
'broadcast' indicates a 'sounds like' (homophone) clue (how the word might sound on the radio or TV).
'specks' sounds like 'SPECS'.
'of' is the link.
(Other definitions for specs that I've seen before include "Glasses (sl.)" , "you can see right through them" , "Glasses (informal)" , "shades?" , "Details for designer" .)