Greediest man involved in quarrel (12)
I believe the answer is:
disagreement
'quarrel' is the definition.
(I've seen this before)
'greediest man involved' is the wordplay.
'involved' indicates anagramming the letters (involved can mean confusing or complex).
'greediest'+'man'='greediestman'
'greediestman' anagrammed gives 'DISAGREEMENT'.
'in' is the link.
(Other definitions for disagreement that I've seen before include "Argument" , "dispute" , "Quarrel" , "Conflict" , "Lack of consensus" .)