Evidence in camera? No (8)
I believe the answer is:
negative
'no' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for negative that I've seen before include "Defeatist" , "Reply of denial" , "Not positive - denial" , "Early form of photo" , "Less than zero, minus" .)