Avoid each concealed notion (4)
I believe the answer is:
idea
'notion' is the definition.
(both can mean a thought)
'avoid each concealed' is the wordplay.
'concealed' indicates the answer is hidden within the clue.
'IDEA' is hidden in the letters of 'avoid each'.
(Other definitions for idea that I've seen before include "A suspicion of" , "a wheeze" , "Notion, image" , "Notion, concept" , "Aim" .)