An appealing sort of accent (5)
I believe the answer is:
acute
'sort of accent' is the definition.
(accent acute is a type of accent mark)
'an appealing' is the wordplay.
'an' becomes 'a'.
'appealing' becomes 'cute' (I've seen this before).
'a'+'cute'='ACUTE'
(Other definitions for acute that I've seen before include "Critical: shrewd" , "Canny" , "quick on the uptake" , "Sharp as of mind - or pain" , "Penetrating; accent" .)