Fanatic supports craze often (6)
I believe the answer is:
zealot
'fanatic' is the definition.
(both can mean an extremist)
'supports craze often' is the wordplay.
'supports craze' becomes 'ze' (I can't justify this - if you can you should give a lot more credence to this answer).
'often' becomes 'a lot' (doing something often is doing it a lot).
'ze'+'alot'='ZEALOT'
Can you help me to learn more?
(Other definitions for zealot that I've seen before include "Person militant about a cause" , "Fervent partisan" , "Fanatical believer" , "Fanatic, obsessed person" , "Person full of enthusiasm, a fanatic" .)