It sweeps up or down unaltered? (5)
I believe the answer is:
radar
'it sweeps up or down unaltered?' is the definition.
The definition suggests a singular noun which matches the answer.
This is the entire clue.
Can you help me to learn more?
(Other definitions for radar that I've seen before include "Electronic rangefinder" , "Remote detection system" , "waves to expose foe" , "System that detects and locates distant objects" , "Radio detection system" .)