Related Clues:

• Yeoman's "yes"
• Words heard on bridges
• Main response?
• The primate might be one of 8 down
• Is the primate all at sea yes?
• Yes, that would sound less than human on board
• It's yes for the primate, and for 7 down
• Yes, it's on board that you'll find the primate
• 1 across
• On board one is agreeable to have something subhuman
• How the primate is willing to be on board
• Yes, it's on board for one to monkey with
• When on board, the primate has to obey like this
• On board it is agreeable to have a primate
• The primate is agreeable on board