Butt piercing annoys hipsters (8)
I believe the answer is:
trendies
'hipsters' is the definition.
(hipsters are trendy people)
'butt piercing annoys' is the wordplay.
'butt' becomes 'end' (I've seen this in other clues).
'piercing' means one lot of letters goes inside another (some letters pierce a hole in others).
'annoys' becomes 'tries' (trying can mean annoying).
'end' going into 'tries' is 'TRENDIES'.
(Other definitions for trendies that I've seen before include "Fashionable people" , "Smart people" .)