Teacher shown up, good day for wise guy (5)
I believe the answer is:
rishi
'wise guy' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's a link between them I don't understand?
'teacher shown up good day' is the wordplay.
'teacher' becomes 'sir' (way of addressing a male teacher).
'shown up' says the letters should be written in reverse (in a down clue, letters go up).
'good day' becomes 'hi'.
'sir' back-to-front is 'ris'.
'ris'+'hi'='RISHI'
'for' is the link.
Can you help me to learn more?
(Other definitions for rishi that I've seen before include "holy man" , "Hindu sage or saint" , "Guru" , "Spiritual leader" , "Revered man" .)