  Low-energy dipole (LED) excitations in $^{18}$O were investigated using a
combination of the variation after $K$-projection in the framework of
antisymmetrized molecular dynamics with $\beta$-constraint with the generator
coordinate method. We obtained two LED states, namely, the $1_1^-$ state with a
dominant shell-model structure and the $1_2^-$ state with a large
$^{14}\textrm{C}+\alpha$ cluster component. Both these states had significant
toroidal dipole (TD) and compressive dipole (CD) strengths, indicating that the
TD and CD modes are not separated but mixed in the LED excitations of $^{18}$O.
This is unlike the CD and TD modes for well-deformed nuclei such as $^{10}$Be,
where the CD and TD modes are generated as $K^{\pi}=0^-$ and $K^{\pi}=1^-$
excitations, respectively, in a largely deformed state.
