Came to wonder about sanction (5)
I believe the answer is:
awoke
'came to' is the definition.
(I've seen this before)
'wonder about sanction' is the wordplay.
'wonder' becomes 'awe' (awe is a kind of wonder).
'about' is an insertion indicator.
'sanction' becomes 'ok' (OK is an example).
'awe' going around 'ok' is 'AWOKE'.
(Other definitions for awoke that I've seen before include "Came round" , "Came out of sleep" , "raised" , "Enlivened" , "Came to consciousness" .)