A male singer having trouble with king’s diplomat (10)
I believe the answer is:
ambassador
'diplomat' is the definition.
(ambassador is a kind of diplomat)
'a male singer having trouble with king's' is the wordplay.
'male' becomes 'm' (common abbreviation).
'singer' becomes 'bass' (bass is a kind of singer).
'having trouble with' becomes 'ado' (I can't explain this - if you can you should believe this answer much more).
'king' becomes 'R' (abbreviation for rex, king in Latin).
'a'+'m'+'bass'+'ado'+'r'='AMBASSADOR'
Can you help me to learn more?
(Other definitions for ambassador that I've seen before include "Messenger" , "voice?" , "Senior diplomat" , "Overseas diplomat" , "foreign agent" .)