Miss out Sunday nap (4)
I believe the answer is:
skip
'miss out' is the definition.
(I've seen this before)
'sunday nap' is the wordplay.
'sunday' becomes 's'.
'nap' becomes 'kip' (I've seen this before**).
's'+'kip'='SKIP'
(Other definitions for skip that I've seen before include "Omit - jump over rope" , "(Make a) small jump" , "Receptacle for rubbish" , "Omit - play with rope" , "Pass over, omit" .)