Like pie, or a piece of cake (4)
I believe the answer is:
easy
I believe this is a double definition.
'like pie' is the first definition.
(as in the phrase 'easy as pie')
'a piece of cake' is the second definition.
(I've seen this before)
'or' is the link.
(Other definitions for easy that I've seen before include "Far from hard" , "Posing no difficulty" , "Simple or uncomplicated" , "Straightforward" , "Promiscuous" .)