hi
yes, you can do that
connect the microphone to Apollo Mic Input 1 with Unison Enabled, set the channel output of this channel to a Lineout channel via UA Console, connect this lineout to the input of your compressor, connect the output of your compressor to an Apollo Line In Channel
now you can actually recorded 2 signals at the same time, the normal uncompressed vocal performances from Channel 1 and the compressed channel from the line channel