Thoughts tossed aside (5)
I believe the answer is:
ideas
'thoughts' is the definition.
(idea is a kind of thought)
'tossed aside' is the wordplay.
'tossed' is an anagram indicator.
'aside' anagrammed gives 'IDEAS'.
(Other definitions for ideas that I've seen before include "Brain waves" , "Thoughts, perceptions" , "Brainwaves" , "Theories" , "Aside (anag.)" .)