Ordago means "I bet the whole game at this hand of cards" it is used in the game of the mus. In that context I suppose it means that Clegg set up a defiance to Cameron, you know like saying..." come and get it if you dare".. well that's maybe to physical, It also applies to intellectual challenges like " bet you can't beat me on that and that"

In your phrase, it means a "challenge, defiance, envite" in order to threatening to break up the coalition if he continues with his welfare cuts

Revisando encontré que hace referencia a una respuesta de ataque, a manera de embestida, un poco desproporcionada.

it means a type of play in the card game (mus) you can bet everything what you have. It can be also ''so good, excelent''. In your phrase i think that Clegg ''said everything'' to cameron... i think hahah