More stylish going over line, one who finishes nicely? (8)
I believe the answer is:
polisher
'who finishes nicely?' is the definition.
(to polish can mean to give a finish)
'more stylish going over line one' is the wordplay.
'more stylish' becomes 'posher' ('posh' can be similar in meaning to 'stylish').
'going over' means one lot of letters goes inside another.
'line' becomes 'l'.
'one' becomes 'i' (Roman numeral).
'l'+'i'='li'
'posher' placed around 'li' is 'POLISHER'.
(Other definitions for polisher that I've seen before include "rubber" , "may be French" .)