See small particles in positions (9)

I believe the answer is:

locations

'positions' is the definition.
('location' can be a synonym of 'position')

'see small particles' is the wordplay.
'see' becomes 'lo' (archaic word meaning 'look!').
'small particles' becomes 'cations' (a cation is a type of ion).
'lo'+'cations'='LOCATIONS'

'in' acts as a link.

(Another definition for locations that I've seen is " Places, sites".)

I've seen this clue in The Telegraph.

Want a hint initially instead of a full solution? Install my app