Group develop core tool for onboarding? (9)

I believe the answer is:
gangplank
'group develop core' is the definition.
I can't judge whether this definition defines the answer.
'tool for onboarding?' is the wordplay.
'tool' becomes 'gang' (gang is a kind of tool).
'for' is a charade indicator (letters next to each other).
'onboarding?' becomes 'plank' (I can't explain this - if you can you should believe this answer much more).
'gang'+'plank'='GANGPLANK'
Can you help me to learn more?
(Other definitions for gangplank that I've seen before include "way of leaving Britannia?" , "Way on to ship" , "Boarding bridge" , "Pirates made people walk it" , "way to get on board" .)
