Nearly perfect suggestion (4)
I believe the answer is:
idea
'suggestion' is the definition.
(thesaurus)
'nearly perfect' is the wordplay.
'nearly' means to remove the last letter.
'perfect' becomes 'ideal' ('ideal' can be similar in meaning to 'perfect').
'ideal' with its last letter taken off is 'IDEA'.
(Other definitions for idea that I've seen before include "Suggestion" , "Something imagined in the mind" , "Content of cognition" , "Proposal" , "Clue" .)