How to tune space between key signature and first note?

[Raphael Manfredi]

Hello,

I have a score in A minor (blank key signature) but with a part for a
clarinet in B flat, so there is a key signature in B minor for its part
(2 sharps).

The problem stems from the fact that the notes on the Clarinet parts are
too close to the key signature, whereas of course other parts have ample
room between the clef and the first note since there is no signature.

How can I add a constant offset between the emission of the key signature
and the first note on a staff?

Thanks,
Raphael