When they're switched on you'll see these slight changes (6)
I believe the answer is:
lights
'when they're switched on you'll see these' is the definition.
The definition suggests an adverb but the answer is not.
'slight changes' is the wordplay.
'changes' indicates an anagram.
'slight' is an anagram of 'LIGHTS'.
Can you help me to learn more?
(Other definitions for lights that I've seen before include "Sources of illumination" , "Illuminations or entrails" , "Ignites or illuminates" , "Illuminators; lungs" , "Offal" .)