Piece of cake in outdoor meal? (6)
I believe the answer is:
picnic
I believe this is a double definition.
'piece of cake' is the first definition.
(both can mean something easy)
'outdoor meal?' is the second definition.
(I've seen this before)
'in' is the link.
(Other definitions for picnic that I've seen before include "external courses?" , "Do without" , "Alfresco meal" , "Informal meal in open air for pleasure" , "An outdoor meal for pleasure" .)