Cab’s losing time as something running through wheel (4)
I believe the answer is:
axis
'something running through wheel' is the definition.
(a wheel revolves around an axis)
'cab's losing time' is the wordplay.
'cab's' becomes 'taxi's' (taxi cab).
'losing' suggests deleting specific letters.
'time' becomes 't' (abbreviation).
'taxis' with 't' removed is 'AXIS'.
'as' is the link.
(Other definitions for axis that I've seen before include "Imaginary dividing line" , "Line from N. to S. Pole" , "where wheel turns?" , "Central point of a rotation" , "Imaginary centre of rotation" .)