What does going spare mean in the context?

[svetlana14]

2:04. Does going spare mean there to be available, that is to say, for financing a candidate (like Boris Johnson if he continues to be involved in politics?

 

[emsr2d2]

Yes, in that context, it means "available" or "that you you're not using".

Have you got any sugar going spare? I want to make a cake and I've run out.
He asked me if I had fifty quid going spare. Hah! Not this close to payday, I don't. (quid = pounds sterling (UK currency))
Has anyone got any printer paper going spare? I've only got one sheet left and I need to print ten posters.

Note that in BrE, it also has another meaning - "to be frantic/panicking" or "to be very angry".

I'm going on holiday tomorrow and I can't find my passport. I'm going spare! What if I don't find it?
When she told her boyfriend she was moving to Spain, he went absolutely spare. He never thought she'd actually go without him.

 

[Skrej]

Neither of those usages exist in AmE, so they may be uniquely BrE.

 

[Rover_KE]

Neither of those usages exist in AmE, so they may be uniquely BrE.

That's probably true.

go spare UK informal
to get very upset or angry:
She goes spare if I'm so much as five minutes late.

(Cambridge Advanced Learners' Dictionary)