Break right up — sadly true (7)
I believe the answer is:
rupture
'break' is the definition.
(I know that rupture is a type of break)
'right up sadly true' is the wordplay.
'right' becomes 'r' (common abbreviation).
'sadly' indicates anagramming the letters.
'true' with letters rearranged gives 'ture'.
'r'+'up'+'ture'='RUPTURE'
(Other definitions for rupture that I've seen before include "State of being torn or burst open" , "Burst suddenly" , "'Tear, burst open (7)'" , "Bursting" , "Sudden break or burst in a body part" .)