Sanctioned radical ideals to gain support (9)
I believe the answer is:
legalised
'sanctioned radical ideals to gain support' is the definition.
I can't judge whether this defines the answer.
'ideals to gain support' is the wordplay.
I cannot really understand how this works, but
an anagram of 'ideals' is 'alised' which is present in the answer.
'support' could be 'leg' (leg is a kind of support) and 'leg' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for legalised that I've seen is " no longer considered as criminal".)