Titian's greed stupidly causing break up (12)
I believe the answer is:
disintegrate
'break up' is the definition.
'titian's greed stupidly' is the wordplay.
'stupidly' is an anagram indicator.
'titians'+'greed'='titiansgreed'
'titiansgreed' anagrammed gives 'DISINTEGRATE'.
'causing' is the link.
(Other definitions for disintegrate that I've seen before include "decay" , "Break into little pieces" , "Smash" , "Go to pieces" , "collapse" .)