Briefly go for and steal piece of cake (6)
I believe the answer is:
picnic
'piece of cake' is the definition.
(both can mean something easy)
'briefly go for and steal' is the wordplay.
'briefly' means to remove the last letter.
'go for' becomes 'pick'.
'and' says to put letters next to each other.
'steal' becomes 'nic' (I can't explain this - if you can you should give a lot more credence to this answer).
'pick' with its final letter taken off is 'pic'.
'pic'+'nic'='PICNIC'
Can you help me to learn more?
(Other definitions for picnic that I've seen before include "outing" , "Informal open-air meal" , "is difficult" , "Money for jam" , "Informal meal taken in the open air" .)