Plea to sleep in? So easily achieved! (2,1,5)
I believe the answer is:
on a plate
'so easily achieved' is the definition.
(as in having something handed to you on a plate)
'plea to sleep in?' is the wordplay.
I cannot quite understand how this works, but
'sleep' could be 'nap' (a nap is a short sleep) and 'nap' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for on a plate that I've seen before include "with little effort" , "requiring next to no effort" , "Available without effort - dinner?" , "readily available" , "Informally available without effort - a meal?" .)