Small swivelling wheel on furniture (6)
I believe the answer is:
castor
'small swivelling wheel on furniture' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for castor that I've seen before include "Brother to Pollux" , "Small swivelled wheel fixed to each leg of a piece of furniture" , "Pollux's twin" , "Trolley wheel" , "One star" .)