They take turns on and off (4)
I believe the answer is:
taps
'they' is the definition.
Both the answer and definition are plural nouns.
Maybe there's an association between them I don't understand?
'turns on and off' is the wordplay.
'turns' says the letters should be written backwards.
'on' becomes 'at' (I've seen this in other clues).
'and' is a charade indicator (letters next to each other).
'off' becomes 'ps' (I can't justify this - if you can you should believe this answer much more).
'at' back-to-front is 'ta'.
'ta'+'ps'='TAPS'
'take' is the link.
Can you help me to learn more?
(Other definitions for taps that I've seen before include "The sound of lights out" , "Strikes lightly; eavesdropping devices" , "Exploits" , "Military bugle call at dusk" , "pierces" .)