An avaricious quality, that's understood (6)
I believe the answer is:
agreed
'understood' is the definition.
(thesaurus)
'an avaricious quality' is the wordplay.
I cannot quite understand how this works, but
'an' could be 'a' and 'a' is present in the answer.
The remaining letters 'greed' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for agreed that I've seen before include "Done!" , "acceptable" , "Consented and concurred" , "That's right" , "In harmony" .)