Stylish chapter introduced by Greek letter (4)
I believe the answer is:
chic
'stylish' is the definition.
('chic' can be similar in meaning to 'stylish')
'chapter introduced by greek letter' is the wordplay.
'chapter' becomes 'c'.
'introduced by' means one lot of letters go next to another.
'greek letter' becomes 'chi' (letter from the Greek alphabet).
'c' put after 'chi' is 'CHIC'.
(Other definitions for chic that I've seen before include "Elegantly stylish" , "Elegant and sophisticated" , "Fashionably elegant" , "Smart - elegant - fashionable" , "Stylishness, elegance" .)