Circus man has to telephone teacher (10)
I believe the answer is:
ringmaster
'circus man' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'to telephone teacher' is the wordplay.
'to telephone' becomes 'ring' ('ring' can be a synonym of 'telephone').
'teacher' becomes 'master' (I've seen this before).
'ring'+'master'='RINGMASTER'
'has' is the link.
Can you help me to learn more?
(Other definitions for ringmaster that I've seen before include "showman" , "Circus leader" , "circus performer" , "Circus compere" , "Top top man" .)