Comedian’s “yes” to German upset salesperson (5)
I believe the answer is:
japer
'comedian's' is the definition.
(someone who jests or japes)
'yes to german upset salesperson' is the wordplay.
'yes to german' becomes 'ja' ('yes' in German).
'upset' shows that the letters should be reversed in order.
'salesperson' becomes 'rep' (I've seen this before).
'rep' reversed gives 'per'.
'ja'+'per'='JAPER'
(Other definitions for japer that I've seen before include "joker" , "trickster" , "One jokes" .)