  We perform a comprehensive analysis of the pion-photon transition form factor
$F_{\pi \gamma}(Q^2)$ involving the transverse momentum corrections with the
present CLEO experimental data, in which the contributions beyond the leading
Fock state have been taken into consideration. As is well-known, the leading
Fock-state contribution dominates of $F_{\pi \gamma}(Q^2)$ at large momentum
transfer ($Q^2$) region. One should include the contributions beyond the
leading Fock state in small $Q^2$ region. In this paper, we construct a
phenomenological expression to estimate the contributions beyond the leading
Fock state based on its asymptotic behavior at $Q^2\to0$. Our present
theoretical results agree well with the experimental data in the whole $Q^2$
region. Then, we extract some useful information of the pionic leading twist-2
distribution amplitude (DA) by comparing our results of $F_{\pi \gamma}(Q^2)$
with the CLEO data. By taking best fit, we have the DA moments,
$a_2(\mu_0^2)=0.002^{+0.063}_{-0.054}$, $a_4(\mu_0^2)=-0.022_{-0.012}^{+0.026}$
and all of higher moments, which are closed to the asymptotic-like behavior of
the pion wavefunction.
