Rambling (7)
(Other definitions for erratic that I've seen before include "Deep affection" , "Cartier (anag.)" , "Shifting like Cartier" , "on irregular path" , "Wayward" .)
'rambling' is the definition.
('roam' can be a synonym of 'ramble')
This is the entire clue.
(Other definitions for roaming that I've seen before include "Moving about" , "wandering around" , "Ranging widely" , "Using a mobile on another network" , "Roving" .)