Under starter's orders

Hi all,
I came across the sentence '...under starters orders...'
What exactly does that mean? It comes from the novel 'Tinker, tailor, soldier, spy' from LeCarré, so it might have a relation to the intelligence community.
If anyone can help...
Thanks
MW

Nope, it's from the world of athletics. Before the start of a race, an official called the starter brings the field of competitors to order, preparing them for the imminent start of the race. The traditional phrase then used is "On your marks... get set... go!", except a shot from a starting-pistol will substitute for the word "go" in any serious event. Starter's orders also apply to horse-racing, especially when a track-wide raisable tape is used instead of mechanical stalls.

So, the phrase "under starter's orders" simply means being prepared and waiting for imminent action.