Paths of planets or particles? (6)
I believe the answer is:
orbits
'paths of planets' is the definition.
(I've seen this before)
'or particles?' is the wordplay.
'particles?' becomes 'bits' (I've seen this in another clue).
'or'+'bits'='ORBITS'
(Other definitions for orbits that I've seen before include "Whole rounds" , "Travels in circular path like planet" , "Planetary paths" , "Circulates" , "Paths of satellites around planets" .)