Runs across wanderer (5)
I believe the answer is:
rover
'wanderer' is the definition.
('rover' can be a synonym of 'wanderer')
'runs across' is the wordplay.
'runs' becomes 'r' (cricket abbreviation).
'across' becomes 'over' ('over' can be a synonym of 'across').
'r'+'over'='ROVER'
(Other definitions for rover that I've seen before include "pirate ship" , "A vagrant" , "Vehicle driven remotely over extraterrestrial terrain" , "Wanderer, archery mark" , "Pirate; dog's name" .)