Numbers including crazy folk who can't settle? (6)
I believe the answer is:
nomads
'folk who can't settle?' is the definition.
(nomads move from place to place)
'numbers including crazy' is the wordplay.
'numbers' becomes 'nos' (no. is a kind of number).
'including' indicates putting letters inside.
'crazy' becomes 'mad' (synonyms).
'nos' enclosing 'mad' is 'NOMADS'.
(Other definitions for nomads that I've seen before include "[DRIFTERS]" , "Vagrant peoples" , "Itinerants" , "Damson consumed by rovers" , "Wandering people, roaming tribes" .)