Regret disrespectful talk holds objective back (7)
I believe the answer is:
sadness
'regret' is the definition.
(I've seen this before)
'disrespectful talk holds objective back' is the wordplay.
'disrespectful talk' becomes 'sass' (I've seen this in another clue).
'holds' is an insertion indicator.
'objective' becomes 'end' (both can mean a purpose).
'back' is a reversal indicator.
'end' reversed gives 'dne'.
'sass' placed around 'dne' is 'SADNESS'.
(Other definitions for sadness that I've seen before include "Grief" , "no joy there" , "Misery" , "Sorrow, unhappiness" , "Dejection" .)