Use a nanny cam, say (3)
I believe the answer is:
spy
'use a nanny cam say' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for spy that I've seen before include "Keep watch secretly, maybe for foreign government" , "Mole, agent" , "Undercover agent" , "One gathers information on enemies" , "Catch sight of" .)