It's apt to be turned on (3)
I believe the answer is:
tap
'it's apt to be turned on' is the definition.
I can't judge whether this definition defines the answer.
'it's apt to be turned' is the wordplay.
'to be turned' indicates anagramming the letters.
'apt' is an anagram of 'TAP'.
Can you help me to learn more?
(Other definitions for tap that I've seen before include "Hit; bug" , "Knock or draw upon" , "Bugging device" , "milk" , "Water source; take advantage of" .)