Keep holding note, intermittently acerbic, for old newsreader (4,5)
I believe the answer is:
town crier
'for old newsreader' is the definition.
(someone who delivered news in the past)
'keep holding note intermittently' is the wordplay.
'keep' becomes 'tower' (keep can mean a fortified structure).
'holding' is an insertion indicator.
'note' becomes 'n' (abbreviation).
'intermittently' becomes 'cri' (I can't explain this - if you can you should give a lot more credence to this answer).
'n'+'cri'='ncri'
'tower' enclosing 'ncri' is 'TOWN-CRIER'.
'acerbic' acts as a link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for town crier that I've seen before include "He would have publicised" , "Formerly, an official who made public announcements" , "'The person who used to make public announcements in the streets (4,5)'" , "Bellman" , "old teller" .)