Possible Clues:

• Suffix for 'class' or 'room'
• ___ in three (chess challenge)
• Chess master's triumphant cry
• First ___ (Gilligan's post)
• Chess conclusion, informally
• End of a match
• Win at the board
• Partner of characters involved in street amusements set-up
• Ram, for a ewe
• Chess ending; pal