Part of speech idealists rebuke (5)
I believe the answer is:
chide
'rebuke' is the definition.
(I know that rebuke can be written as chide)
'part of speech idealists' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'CHIDE' can be found hidden inside 'speech idealists'.
(Other definitions for chide that I've seen before include "Rebuke, scold" , "Tear off strip" , "Censure, berate" , "Tell off" , "Admonish" .)