Worked topless, like a smooth-running machine (5)
I believe the answer is:
oiled
'like a smooth-running machine' is the definition.
(I've seen this in another clue)
'worked topless' is the wordplay.
'worked' becomes 'toiled' (toiling is a kind of working).
'topless' means to remove the first letter.
'toiled' with its initial letter taken away is 'OILED'.
(Other definitions for oiled that I've seen before include "Oldie (anag)" , "Lubricated (with drink?)" , "get drunk" , "Cut" , "protected from rust?" .)