Half of them get into bed earlier; sadly these can't be reformed (12)
I believe the answer is:
irredeemable
'these can't be reformed' is the definition.
The definition suggests an adverb but the answer is not.
'half of them get into bed earlier sadly' is the wordplay.
'half of' suggests halving the letters.
'get into' is an insertion indicator.
'sadly' is an anagram indicator.
'them' with half the letters taken is 'em'.
'bed'+'earlier'='bedearlier'
'bedearlier' with letters rearranged gives 'irredeable'.
'em' inserted within 'irredeable' is 'IRREDEEMABLE'.
Can you help me to learn more?
(Other definitions for irredeemable that I've seen before include "Not able to be saved" , "Without a pawn ticket, things can be so" , "Beyond being saved" , "hopeless" .)