In the morning, power electronic device (3)
I believe the answer is:
amp
'electronic device' is the definition.
(amplifier)
'in the morning power' is the wordplay.
'in the morning' becomes 'am' (short for ante meridiem - before noon).
'power' becomes 'p' (symbol in physics).
'am'+'p'='AMP'
(Other definitions for amp that I've seen before include "Map of electric current" , "sound is increased by this" , "Map about electric unit" , "In short, unit for measuring electric current" , "Device making sound louder" .)