He wanders right across (5)
I believe the answer is:
rover
'he wanders' is the definition.
(I've seen this in another clue)
'right across' is the wordplay.
'right' becomes 'r' (common abbreviation).
'across' becomes 'over' (synonyms).
'r'+'over'='ROVER'
(Other definitions for rover that I've seen before include "Nomad" , "one in Bristol, one in Doncaster, perhaps" , "Vehicle driven remotely over extraterrestrial terrain" , "rambler" , "Old scout" .)