Happened to be a piece of cake for me (4)
I believe the answer is:
came
'happened' is the definition.
(to happen upon and to come upon mean to encounter)
'a piece of cake for me' is the wordplay.
'a piece of' says to take the initial letters.
'for' is a charade indicator (letters next to each other).
'me' becomes 'ame' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The initial letter of 'cake' is 'c'.
'c'+'ame'='CAME'
'to be' is the link.
Can you help me to learn more?
(Other definitions for came that I've seen before include "Appeared" , "Arrived" .)