Im not too sure of the definition on this appledumplin .
In Chambers it gives Tana as a police or military station ( in India ) . So it seems to be the obvious answer .
I was confuddled myself over what a deputy PM has to do with it :)
Tanaiste is the term for the deputy PM of the Republic of Ireland (like Taoiseach for the Irish PM) A bit obscure but not unduly so by Spectator standards!
Hard to give a clue really .
They are
C'est la fin des haricots
C'est chou vert et vert chou
Manger son bl� en herbe
and were hard to find without Brewers !