riddle - What am I? (Answer may be superfluous)

I start with a fight, or a chance to relax,
And end with a cut, and am but you what.
In between I am quite average,
But overall you hope I am never required.

What am I?

Answer

A thought is you are a

spare

I start with a fight, or a chance to relax,

start with a fight - spar, or a chance to relax - spa,

And end with a cut, and am but you what.

end with a cut - pare, and am but you what : I am but you are.

In between I am quite average,

par

But overall you hope I am never required.

something you keep as a spare like a tyre.

Title: Answer may be superfluous

it may not be needed.