It measures nothing less than a shooting star! (5)
I believe the answer is:
meter
'it measures' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for meter that I've seen before include "Device for measuring and recording" , "Something measuring" , "Measuring device as for electricity usage (5)" , "Device that measures, say, electricity usage" , "Device for recording, say, usage (5)" .)