An appealing sort of angle (5)
I believe the answer is:
acute
'sort of angle' is the definition.
'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 "Shrewd; serious" , "Perspicacious" , "not seen in cafe here!" , "feature at the beginning and end of a French summer" , "Short and severe" .)