Allows to rest peacefully? Not really! (4,3)
I believe the answer is:
lets rip
'not really' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'allows to rest peacefully?' is the wordplay.
'allows to' becomes 'lets' (I've seen this in another clue).
'rest peacefully?' becomes 'RIP' (rest in peace).
'lets'+'rip'='LETS RIP'
Can you help me to learn more?
(Other definitions for lets rip that I've seen before include "puts his foot down" , "Vigorously proceeds" .)