___ Armstrong, jazz musician (5)
I believe the answer is:
louis
I believe this is a double definition.
'armstrong' is the first definition.
(I've seen this in another clue)
'jazz musician' is the second definition.
(I know that Louis is a jazz musician)
(Other definitions for louis that I've seen before include "Many kings of France" , "-- Armstrong, trumpeter" , "French gold coin" , "French boy's name" , "Joe ---, the Brown Bomber" .)