A group of directors on a ship? (6)
I believe the answer is:
aboard
'on a ship' is the definition.
(I've seen this before)
'a group of directors' is the wordplay.
'group of directors' becomes 'board' (board of directors).
'a'+'board'='ABOARD'
(Other definitions for aboard that I've seen before include "on a ferry?" , "at sea, say?" , "on base" , "on a liner, say" , "on boat, perhaps" .)