The most common and most likely answer to this crossword clue is the 3 plus 5 letter word ALT RIGHT
A
L
T
R
I
G
H
T
Buddy explains!

The straight part
We know that "Extreme political group" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case extreme political group = alt right.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ALT RIGHT mean?
ALT RIGHT noun- An amorphous group of right-wing ideologies opposed to multiculturalism and egalitarianism by race and sex, mostly active on the Internet; often supportive of anti-Semitism, Islamophobia, homophobia, transphobia, white nationalism and white supremacy, adherence to which is sometimes claimed to be ironic.
- (chiefly US) A member of the alt-right; an alt-righter.
- Of or pertaining to the alt-right.