You can push it (especially uphill?) (4)
I believe the answer is:
bike
'you can' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for bike that I've seen before include "Two-wheeler (abbr)" , "Take a ride" , "See 5" , "Cycle (colloq.)" , "vehicle" .)