Rebuke such ideas — but not all (5)
I believe the answer is:
chide
'rebuke' is the definition.
(I know that rebuke can be written as chide)
'such ideas but not all' is the wordplay.
'not all' says the answer is hidden in the clue (only some of the letters).
'CHIDE' is hidden within 'such ideas but'.
(Other definitions for chide that I've seen before include "lecture" , "Seeing scold" , "Reprove" , "Censure angrily" , "Tell off" .)