Mad hairstyle for extremists (7,6)
I believe the answer is:
lunatic fringe
'extremists' is the definition.
(I've seen this in another clue)
'mad hairstyle' is the wordplay.
'mad' becomes 'lunatic' (I've seen this before).
'hairstyle' becomes 'fringe' ().
'lunatic'+'fringe'='LUNATIC FRINGE'
'for' is the link.
(Other definitions for lunatic fringe that I've seen before include "Extreme fanatics" , "Extreme members of group" , "Extreme political element" , "fruitcakes around the edge?" , "People who support extreme views" .)