Literally less than perfect plan (4)
I believe the answer is:
idea
'plan' is the definition.
(both can mean an intention)
'literally less than perfect' is the wordplay.
'literally' becomes 'ide' (I can't justify this - if you can you should believe this answer much more).
'less than' means to remove the last letter (not the full word).
'perfect' becomes 'ai' (resembles Ai, informal term meaning excellent).
'ai' with its last letter taken off is 'a'.
'ide'+'a'='IDEA'
Can you help me to learn more?
(Other definitions for idea that I've seen before include "Flash of inspiration?" , "Thought or notion (4)" , "A suspicion of" , "Thought, belief" , "Notion, concept" .)