  The inclusive decay rate into pions of the charmed $D_s$ meson is
surprisingly larger than estimates expected from the $W$ annihilation, adopting
commonly used values of current-algebra up and down quark masses. We then go
beyond this tree diagram and consider possible QCD effects that might cause
such a large rate. There are two; the first one is related to the spectator
decay $ c{\bar s} \rightarrow s{\bar s} + u {\bar d}$ followed by $ s {\bar s}
\rightarrow d{\bar d}~,~ u{\bar u}$ via two-gluon exchange box diagram. The
second one is a gluon emission in weak annihilation for which the usual
helicity suppression is vitiated: $D_s\rightarrow W+g$ followed by $
W\rightarrow u {\bar d},~ g\rightarrow d{\bar d},~u{\bar u}$. These two
contributions, however, turn out to be insufficient to explain data, implying
that the puzzle could be understood if the up, down quarks have higher mass
values. Furthermore, on the basis of experimental informations on the spectral
function $\rho_{3\pi}(Q^2)$ deduced from the exclusive $ D_s \rightarrow 3\pi$
mode, the QCD sum rules also point to a higher mass for light quarks.
