Butch Cassidy finally goes after chap heading for Louisiana (5)
I believe the answer is:
manly
'butch' is the definition.
'cassidy finally goes after chap heading for louisiana' is the wordplay.
'finally' suggests the final letters.
'goes after' is a charade indicator (letters next to each other).
'chap' becomes 'man' (I've seen this before).
'heading for' suggests taking the first letters.
The final letter of 'cassidy' is 'y'.
The initial letter of 'louisiana' is 'l'.
'man'+'l'='manl'
'y' put after 'manl' is 'MANLY'.
(Other definitions for manly that I've seen before include "With male attributes" , "Befitting a male" , "Masculine" , "Bold" , "Virile" .)