  Variable red- and blue-shifted absorption features observed in the Ca ii K
line towards the A-type shell star $\phi$ Leo have been suggested by us in a
previous work to be likely due to solid, comet-like bodies in the circumstellar
(CS) environment. Our aim is to expand our observational study of this object
to other characteristic spectral lines of A-type photospheres as well as to
lines arising in their CS shells. We have obtained more than 500
high-resolution optical spectra collected at different telescopes from December
2015 to January 2019. We have analysed some photospheric lines, in particular
Ca i 4226 \AA ~and Mg ii 4481 \AA, as well as the circumstellar shell lines Ca
ii H\&K, Ca ii IR triplet, Fe ii, Ti ii, and the Balmer lines H$\alpha$ and
H$\beta$. Our observational study reveals that $\phi$ Leo is a variable
$\delta$ Scuti star whose spectra show remarkable dumps and bumps superimposed
on the photospheric line profiles, which vary their strength and sharpness,
propagate from blue- to more red-shifted radial velocities and persisting
during a few hours, likely produced by non-radial pulsations. At the same time,
all shell lines present an emission at $\sim$3 km/s centered at the core of the
CS features, and two variable absorption minima at both sides of the emission.
The variations observed in the Ca ii H\&K, Fe ii and Ti ii lines occur at any
time scale from minutes to days and observing run, but without any clear
correlation or recognizable temporal pattern among the different lines. In the
case of H$\alpha$ the CS contribution is also variable in just one of the
observing runs. We suggest that $\phi$ Leo is a rapidly rotating $\delta$ Scuti
star surrounded by a variable, (nearly) edge-on CS disk possibly re-supplied by
the $\delta$ Scuti pulsations.
