Psychiatrist's answer to "Is he sane to keep wandering the world?" (5)
I believe the answer is:
nomad
This could be a double definition.
'psychiatrist's answer to is he sane to keep' is the first definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'wandering the world?' is the second definition.
'nomad' can be an answer for 'wandering' (I've seen this before). I am not certain of the 'the world?' bit.
Can you help me to learn more?
(Other definitions for nomad that I've seen before include "A member of a wandering tribe" , "Member of travelling people" , "A wandering tribesman" , "Person always on the move" , "Traveller with no permanent home" .)