Royal Marine crosses Roman road in high spirits (8)
I believe the answer is:
jovially
'royal marine crosses roman road in high spirits' is the definition.
I can't judge whether this defines the answer.
'royal marine crosses roman road' is the wordplay.
'royal marine' becomes 'jolly'.
'crosses' means one lot of letters goes inside another.
'roman road' becomes 'via' (I've seen this in another clue).
'jolly' placed around 'via' is 'JOVIALLY'.
Can you help me to learn more?
(Other definitions for jovially that I've seen before include "In a cheerful and friendly manner" , "In a jolly and friendly manner" .)