to 2346: the name of the game

The unclued entries are all names for pontoon; extra words in 27, 31, 33, 34 and 36 needed the letters S, G, O, U, R to become WHIST, BRIDGE, SOLO, AUCTION, CONTRACT. Auction, auction bridge, bridge, bridge whist, contract, contract bridge, solo, solo whist and whist are all card-games listed in Chambers. PONTOON is a BRIDGE.
 
First prize Rhiannon Hales, Ilfracombe, Devon
Runners-up John Renwick, Ramsgate, Kent;
R. Dickinson, Lewes, East Sussex