Taxi ticker (5)
I believe the answer is:
meter
'taxi ticker' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for meter that I've seen before include "Device that measures, say, electricity usage" , "Gauge" , "Measuring device as for electricity usage (5)" , "Measuring device as for electricity consumption" , "Device for measuring and recording" .)