Male history teacher?
I believe the answer is:
past master
'male' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'history teacher?' is the wordplay.
'history' becomes 'past' (I've seen this before**).
'teacher?' becomes 'master' (I've seen this before).
'past'+'master'='PAST-MASTER'
Can you help me to learn more?
(Other definitions for past master that I've seen before include "Someone with a long and thorough experience in a given activity" , "seen at staff reunions?" , "Adept fellow" , "Person experienced in a particular field" , "wizard" .)