Caustic joke on posh man (7)

I believe the answer is:

pungent

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'caustic' is the definition.
(I've seen this before)

'joke on posh man' is the wordplay.
'joke' becomes 'pun' (pun is a type of joke).
'on' says to put letters next to each other.
'posh man' becomes 'gent' (gent is a kind of man. I am not sure about the 'posh' bit.).
'pun'+'gent'='PUNGENT'

Can you help me to learn more?

(Other definitions for pungent that I've seen before include "With a sharp taste or smell" , "spicy" , "Incisive" , "Biting" , "delivering powerful smack" .)

I've seen this clue in The Sun.

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