A WORD OF TEN LETTERS

I'm a word of ten letters,

But what a surprise!

I'm pronounced as five of them,

Just one-half that size.

My first is found when a spouse isn't around;

When a couple split, each may be called this.

My second has one where normally two form a pair;

You'll get the nod if you look in a pod.

My third and my fifth a capital denote,

Whose chief resident is determined by vote.

Reversed they form a pair, alphabetically speaking,

And also hold music - if it's a disc you are seeking.

My fourth you will find in both pencil and pen,

In the middle of end and the end of men.

Answer:

EXPEDIENCY - pronounced X P D N C

X = ex

P = pea (two peas in a pod)

DC = Washington, D.C. - home of the President

CD = alphabetical pair/music disc

N = eNd/meN