  The origin of the large $\alpha$ particle production and incomplete fusion in
reactions involving weakly-bound $\alpha$+$x$ cluster nuclei still remains
unresolved. While the (two-step) process of breakup followed by capture of the
``free" complementary fragment ($x$) is widely believed to be responsible, a
few recent studies suggest the dominant role of (direct) cluster stripping. To
achieve an unambiguous experimental discrimination between these two processes,
a coincidence measurement between the outgoing $\alpha$ particles and $\gamma$
rays from the heavy residues has been performed for the
$^7$Li($\alpha$+triton)+$^{93}$Nb system. Proper choice of kinematical
conditions allowed for the first time a significant population of the region
accessible only to the direct triton stripping process and not to breakup
followed by the capture of the ``free'' triton (from the three-body continuum).
This result, also supported by a cluster-transfer calculation, clearly
establishes the dominance of the direct cluster-stripping mechanism in the
large alpha production.
