Sanction that hurt everyone at first (5)
I believe the answer is:
allow
'sanction' is the definition.
(thesaurus)
'that hurt everyone at first' is the wordplay.
'that hurt' becomes 'ow' (I've seen this in other clues).
'everyone' becomes 'all' (I've seen this before).
'at first' means one lot of letters go next to another.
'ow' put after 'all' is 'ALLOW'.
(Other definitions for allow that I've seen before include "Permit, let happen" , "brook" , "Admit as acceptable" , "Permit or acknowledge" , "Grant" .)