PA system doesn't start to irritate (5)
I believe the answer is:
annoy
'to irritate' is the definition.
(synonyms)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for annoy that I've seen before include "eat" , "Exasperate" , "trouble" , "Irritate, nettle" , "get angry" .)