Aide's unusual impressions (5)
I believe the answer is:
ideas
'impressions' is the definition.
(I've seen this in another clue)
'aide's unusual' is the wordplay.
'unusual' indicates anagramming the letters.
'aides' is an anagram of 'IDEAS'.
(Other definitions for ideas that I've seen before include "Notions, thoughts" , "Thoughts, maybe creative" , "Brain waves" , "plans" , "Thoughts or opinions" .)