I already asked how to embed fonts from Dejavu Sans Extralight in Lates documents. This is the link to my original question : DejaVu Sans Light with XeLaTeX?
None the less, the character U+2C7A (an O with a ring INside) is being displayed a blank square. I picked the letter via Kcharselect, so it exists. It is in the plane Latin -Extended C
Do I have a conflict with \usepackage[T1]{fontenc} , that is do I need a different encoding?
minimum working example, as suggested :
\documentclass[english]{article}
\usepackage{centernot}
\usepackage{fontspec}
\usepackage{natbib}
\usepackage{graphicx}
\usepackage{xunicode}
\usepackage{xltxtra}
\usepackage{mathrsfs}
\usepackage{mathtools}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{newtxtext}
\usepackage{newtxmath}
\newfontfamily\urw{URW Gothic L}
\DeclareTextFontCommand{\murw}{\urw}
\newfontfamily\dej{DejaVu Sans ExtraLight}
\DeclareTextFontCommand{\mdej}{\dej}
\include{./symbols}
\usepackage{babel}
\begin{document}
math example :$\Dorbit$
normal : \dorbit
\end{document}
in symbols.tex
\newcommand{\Dorbit}{\mdej{ⱺ}}
fontenc
with XeLaTeX. I get the glyph, if I add it to the MWE in my answer to your previous question.