Knock a big town for its greediness (8)
I believe the answer is:
rapacity
'greediness' is the definition.
(I've seen this in another clue)
'knock a big town' is the wordplay.
'knock' becomes 'rap' (synonyms).
'big town' becomes 'city' (I've seen this before).
'rap'+'a'+'city'='RAPACITY'
'for its' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for rapacity that I've seen before include "Voraciousness" , "Extreme greed and predatory quality" , "Aggressive greed" , "excessive greed" , "Predatory greed and extortion" .)