We're told why Italian sauce's flipping sweet (6)
I believe the answer is:
sugary
'sweet' is the definition.
(similar in meaning)
'we're told why italian sauce's flipping' is the wordplay.
'we're told' indicates a 'sounds like' (homophone) clue.
'italian sauce's' becomes 'ragu's'.
'flipping' is a reversal indicator.
'why' is a homophone of 'y'.
'y'+'ragus'='yragus'
'yragus' backwards is 'SUGARY'.
(Other definitions for sugary that I've seen before include "Sweet, perhaps too much so" , "Sweet, syrupy" , "Over-sentimental" , "Excessively sweet or saccharine" , "Excessively sentimental" .)