No - crazy is the beginning of mind wandering (8)
I believe the answer is:
'wandering' is the definition.
'no crazy is the beginning of mind' is the wordplay.
'crazy' becomes 'mad' ('mad' can be a synonym of 'crazy').
'the beginning of' indicates taking the first letters.
The initial letter of 'mind' is 'm'.
(Other definitions for nomadism that I've seen before include "wandering" , "The state of moving from place to place with no permanent home" , "The Bedouin, say, practise it" .)