Instrument to finish with zero range (9)
I believe the answer is:
endoscope
'instrument' is the definition.
(endoscope is a kind of instrument)
'finish with zero range' is the wordplay.
I cannot really see how this works, but
'finish' could be 'end' (synonyms) and 'end' is present in the answer.
'zero' could be 'o' (O resembles 0) and 'o' is present in the answer.
'range' could be 'scope' (synonyms) and 'scope' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'to' acts as a link.
Can you help me to learn more?
(Other definitions for endoscope that I've seen before include "Instrument for viewing internal body cavities and organs" , "medical device" , "Unwelcome camera" , "Medical instrument" , "medical probe" .)