Attractive person’s style, extremely immaculate (5)
I believe the answer is:
cutie
'attractive person's' is the definition.
(I've seen this before)
'style extremely immaculate' is the wordplay.
'style' becomes 'cut' (synonyms).
'extremely' says to hollow out the word (remove centre letters).
'immaculate' with its centre taken out is 'ie'.
'cut'+'ie'='CUTIE'
(Other definitions for cutie that I've seen before include "an attractive thing" , "Smart female" , "lovely" , "Attractive person or animal" , "Attractive young woman (slang)" .)