  It has been shown experimentally that the $^6$Li nucleus shrinks by adding a
$\Lambda$ particle while its spectrum is also compressed. We discuss the
compatibility of these two effects, contrasting also with a relation between
the shrinkage effect and the stability of the spectrum in the $^9_\Lambda$Be
hypernucleus. To this end, we employ two-body $d$-$^5_\Lambda$He and
$\alpha$-$^5_\Lambda$He cluster models for the $^7_\Lambda$Li and
$^9_\Lambda$Be hypernuclei, respectively. We first argue that a Gaussian-like
interaction between two clusters leads to a stabilization of the spectrum
against an addition of a $\Lambda$ particle, even though the intercluster
distance is reduced. In the case of $^7_\Lambda$Li, the spin-orbit interaction
between the intercluster motion and the deuteron spin has to be considered
also. We show that the shrinkage effect makes the expectation value of the
spin-orbit potential larger, lowering the excitation energy for the
$^6$Li($3^+)\otimes \Lambda(1/2^+)$ level.
