Audio problem
I believe the answer is:
'audio problem' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for echo that I've seen before include "Sound bouncing back" , "She loved Narcissus - it's recalled" , "Rebounding sound" , "A natural sound reflection" , "Nymph whose love Narcissus spurned" .)