Thin line moving between English and American style (4)
I believe the answer is:
elan
'american style' is the definition.
'elan' can be an answer for 'style' (synonyms). I am not sure about the 'american' bit.
'thin line moving between english and' is the wordplay.
'thin line moving' becomes 'la' (I am not sure about this - if you are sure you should believe this answer much more).
'between' means one lot of letters goes inside another.
'english' becomes 'E' (abbreviation).
'and' becomes 'n' (common abbreviation for 'and').
'e'+'n'='en'
'la' inserted within 'en' is 'ELAN'.
Can you help me to learn more?
(Other definitions for elan that I've seen before include "Impetuosity - style" , "Dash and enthusiasm." , "Vigour, style, enthusiasm" , "Dashing style" , "Vivacity, dash" .)