By the sound of it, panel fed up (5)
I believe the answer is:
bored
'fed up' is the definition.
(fed up can mean bored)
'by the sound of it panel' is the wordplay.
'by the sound of it' shows a homophone (sound like).
'panel' becomes 'board' (synonyms).
'board' sounds like 'BORED'.
(Other definitions for bored that I've seen before include "Brassed off" , "Weary; drilled" , "Fed up - tired of the world" , "Feeling weary and uninterested" , "Drilled (a hole)" .)