
\begin{tikzpicture}
\draw[thin,dashed,<->] (0.5,0) to (7.5,0);
\coordinate (a) at (1,0);
\coordinate (b) at (3,0);
\coordinate (c) at (5,0);
\coordinate (d) at (7,0);
\draw (a) to[bend left=80] (c);
\draw (b) to[bend left=80] (d);
\clip (a) to [bend left=80] (c) -- cycle;
\fill[yellow] (b) to[bend left=80] (d) -- cycle;
\node (x) at (4,0.3) {\small here};
\end{tikzpicture}
Update
In the above solution the right edge of the yellow region is thinner, due to the clipping. It can be solved if the arcs are drawn after the yellow fill. It is neccesary to use a scope to "undo" the clipping when drawing the arcs:

\begin{tikzpicture}
\draw[thin,dashed,<->] (0.5,0) to (7.5,0);
\coordinate (a) at (1,0);
\coordinate (b) at (3,0);
\coordinate (c) at (5,0);
\coordinate (d) at (7,0);
\begin{scope}
\clip (a) to [bend left=80] (c) -- cycle;
\fill[yellow] (b) to[bend left=80] (d) -- cycle;
\end{scope}
\draw (a) to[bend left=80] (c);
\draw (b) to[bend left=80] (d);
\node (x) at (4,0.3) {\small here};
\end{tikzpicture}
Update 2: Look ma, no clipping!
And of course this is big cheating. Just for fun.
\begin{tikzpicture}
\draw[thin,dashed,<->] (0.5,0) to (7.5,0);
\coordinate (a) at (1,0);
\coordinate (b) at (3,0);
\coordinate (c) at (5,0);
\coordinate (d) at (7,0);
\fill[yellow]
(a) to[bend left=80] (c);
\fill[white, even odd rule]
(a) to[bend left=80] (c) -- (b) to[bend left=80] (d);
\draw (a) to[bend left=80] (c);
\draw (b) to[bend left=80] (d);
\node (x) at (4,0.3) {\small here};
\end{tikzpicture}

clip. – Jake Feb 27 at 22:35