Sure. But how you'd do it, will depend on details of
what you want from this.
You could cut power (a load switch IC or two) and
this would save a fair bit of current from the quiet
VCO supply. But there are issues with the turnon
and turnoff behaviors, are there chirps and pops on
audio or radio (whatever the application might be)?
How long does the VCO take from power-on to
stable and right? Maybe you want to isolate the
VCO's output and ground the downstream amplifier
input before cutting PA power, but keep the VCO
alive and on an even keel if it's a critical frequency
reference (op amp VCO, I kinda doubt; just illustrating
a general point).
Whatever you want to do can probably be done.
There's power management and signal switching
chip solutions galore and the problem is choosing.
Like they say in the movies, "happiness consists
of wanting the right things".