It may be a piece of cake (5)
I believe the answer is:
slice
'it may' is the definition.
The definition suggests a singular noun which matches the answer.
'a piece of cake' is the wordplay.
'a piece of' becomes 'sl' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'cake' becomes 'ice' (I have seen 'Top cake' mean 'ice' so perhaps 'cake' could also mean 'ice').
'sl'+'ice'='SLICE'
'be' acts as a link.
Can you help me to learn more?
(Other definitions for slice that I've seen before include "shot in golf that goes astray" , "poor golf shot" , "Spin" , "Serving cut from a larger portion" , "Portion of pizza" .)