A piece of cake each — extremely scrummy (4)
I believe the answer is:
easy
'a piece of cake' is the definition.
(I've seen this in another clue)
'each extremely scrummy' is the wordplay.
'each' becomes 'ea' (abbreviation).
'extremely' suggests removing the centre (only the extremes of the word are used).
'scrummy' with its centre removed is 'sy'.
'ea'+'sy'='EASY'
(Other definitions for easy that I've seen before include "careful!" , "Requiring little effort" , "Like a walk in the park?" , "Not rocket science" , "Promiscuous" .)