Speaker -- one's barking! (6)
I believe the answer is:
woofer
'speaker' is the definition.
(woofer is a kind of speaker)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for woofer that I've seen before include "sound booster?" , "Bass loudspeaker" , "Loudspeaker that reproduces lower frequency sounds" , "Low-frequency speaker" , "Lab possibly" .)