Roman emperor good with Scotland (5)
I believe the answer is:
galba
'roman emperor' is the definition.
(I've seen this in another clue)
'good with scotland' is the wordplay.
'good' becomes 'g' (abbreviation).
'with' is a charade indicator (letters next to each other).
'scotland' becomes 'Alba' (Gaelic name for Scotland).
'g'+'alba'='GALBA'
(Other definitions for galba that I've seen before include "Emperor in sisty eight AD" , "successor to Nero" .)