Diplomat, a male, so sad, drunk in pub (10)
I believe the answer is:
ambassador
'diplomat' is the definition.
(ambassador is a kind of diplomat)
'a male so sad drunk in pub' is the wordplay.
'a male' becomes 'am' (I've seen this in other clues**).
'drunk' is an anagram indicator.
'in' indicates putting letters inside.
'pub' becomes 'bar' (I've seen this before).
'so'+'sad'='sosad'
'sosad' with letters rearranged gives 'ssado'.
'ssado' put inside 'bar' is 'bassador'.
'am'+'bassador'='AMBASSADOR'
(Other definitions for ambassador that I've seen before include "accredited diplomat" , "High-ranking diplomat" , "Senior diplomat" , "Overseas envoy" , "Foreign representative" .)