Piercing sort of accent? (5)
I believe the answer is:
acute
I believe this clue is a double definition.
'piercing' is the first definition.
(I know that piercing can be written as acute)
'sort of accent?' is the second definition.
(I've seen this before)
(Other definitions for acute that I've seen before include "Sharp; severe" , "Discerning" , "Sharp or crucial" , "quick on the uptake" , "Perspicacious" .)