A snake on the road and on to a vessel (6)

I believe the answer is:

aboard

I'm a little stuck... Click here to teach me more about this clue!

'on to a vessel' is the definition.
I can't tell whether this defines the answer.

'a snake on the road' is the wordplay.
'snake' becomes 'boa' (boa constrictor, type of snake).
'on' is a charade indicator (letters next to each other).
'the road' becomes 'rd' (abbreviation).
'a'+'boa'+'rd'='ABOARD'

'and' is the link.

Can you help me to learn more?

(Other definitions for aboard that I've seen before include "On vessel or vehicle" , "On (eg, a ship)" , "On an aircraft" , "Joined for mutual benefit" , "... [CRUISE SHIP] here, perhaps" .)

I've seen this clue in the Sydney Morning Herald.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.