Teacher's answer to all brain locks? (6,3)
I believe the answer is:
master key
'to all brain locks?' is the definition.
I can't judge whether this definition defines the answer.
'teacher's answer' is the wordplay.
'teacher' becomes 'master' (I've seen this before).
'answer' becomes 'key' (I can't explain this - if you can you should give a lot more credence to this answer).
'master'+'key'='MASTER-KEY'
Can you help me to learn more?
(Other definitions for master key that I've seen before include "one readily admits!" , "Locker" , "All-round opener" , "needed for Common Entrance?" , "Passe-partout" .)