Time machine (5)
I believe the answer is:
clock
'time machine' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for clock that I've seen before include "Hit" , "how to falsify car's mileage" , "'Rock Around the --', 1956 film" , "Timepiece" , "Use for seed head of a dandelion?" .)