Suspect let cop see instrument (9)
I believe the answer is:
telescope
'instrument' is the definition.
(telescope is a kind of instrument)
'suspect let cop see' is the wordplay.
'suspect' indicates anagramming the letters (a suspicious or unusual spelling).
'let'+'cop'+'see'='letcopsee'
'letcopsee' is an anagram of 'TELESCOPE'.
(Other definitions for telescope that I've seen before include "Instrument for viewing from afar" , "Optical instrument for distant viewing" , "Compress like optical instrument that magnifies" , "contract" , "Magnifier of distant images" .)