A lust that's understood (6)
I believe the answer is:
agreed
'understood' is the definition.
(thesaurus)
'a lust' is the wordplay.
I cannot really see how this works, but
'a' is found in the answer.
The remaining letters 'greed' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'that's' is the link.
Can you help me to learn more?
(Other definitions for agreed that I've seen before include "Consented and concurred" , "That's right" , "Accorded" , "Did concur" , "acceptable" .)