So the Americans had a famous bandmaster (5)
I believe the answer is:
sousa
'famous bandmaster' is the definition.
The definition suggests a singular noun which matches the answer.
'so the americans had a' is the wordplay.
'the americans' becomes 'us' (I can't explain this - if you can you should believe this answer much more).
'had' says to put letters next to each other.
'so'+'us'+'a'='SOUSA'
Can you help me to learn more?
(Other definitions for sousa that I've seen before include "US composer of marches" , "US march king" , "Composer of "The Stars and Stripes Forever"" , "he produced the Washington Post" , "John Philip -, composer of famous marches (The Stars and Stripes for Ever)" .)