Nasty critic part-needling patron (9)

I believe the answer is:

backbiter

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'nasty critic' is the definition.
'backbiter' can be an answer for 'critic' (I've seen this before). I am unsure of the 'nasty' bit.

'part-needling patron' is the wordplay.
'part' becomes 'back' (back is a kind of part).
'needling patron' becomes 'biter' (I can't justify this - if you can you should believe this answer much more).
'back'+'biter'='BACKBITER'

Can you help me to learn more?

(Other definitions for backbiter that I've seen before include "bitchy type" , "Spiteful person" , "Slanderer, maligner" , "One attacks the reputation of another" , "Spiteful speaker" .)

I've seen this clue in the Sydney Morning Herald.

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