Fit to bust, tart somehow gets revenge (3,3,3)
I believe the answer is:
tit for tat
'revenge' is the definition.
(I've seen this before)
'fit to bust tart somehow' is the wordplay.
'bust' indicates anagramming the letters.
'somehow' is an anagram indicator.
'fit'+'to'='fitto'
'fitto' anagrammed gives 'titfo'.
'tart' with letters rearranged gives 'rtat'.
'titfo'+'rtat'='TIT-FOR-TAT'
'gets' is the link.
(Other definitions for tit for tat that I've seen before include "Retaliation in kind" , "Retaliation for an injury - almost equal" , "An eye for an eye" , "... pork-pie maybe" , "You hit me, I hit you" .)