Creative output is almost perfect (4)
I believe the answer is:
idea
'creative output' is the definition.
(I've seen this in another clue)
'almost perfect' is the wordplay.
'almost' means to remove the last letter (almost the whole word is kept).
'perfect' becomes 'ideal' (similar in meaning).
'ideal' with its last letter removed is 'IDEA'.
'is' acts as a link.
(Other definitions for idea that I've seen before include "Notion, concept" , "Sudden inspiration?" , "Notion, image" , "A suspicion of" , "Mental impression" .)