Get angry at hair (7)
I believe the answer is:
bristle
I believe this clue is a double definition.
'get angry' is the first definition.
(I've seen this before)
'hair' is the second definition.
(I know that bristle is a type of hair)
'at' acts as a link.
(Other definitions for bristle that I've seen before include "rise up" , "A stiff hair on chin" , "Short, tough piece of hair" , "Display anger - stubble" , "React angrily" .)