The easiest way to get the ClamAV package is using Homebrew
$ brew install clamav
Before trying to start the clamd process, you'll need a copy of the ClamAV databases.
Create a freshclam.conf file and configure as so
# /usr/local/etc/clamd.conf
DatabaseMirror database.clamav.net
Then run
$ freshclam -v
to download the ClamAV databases. The output will look something like this:
Current working dir is /usr/local/Cellar/clamav/0.98.1/share/clamav
Max retries == 3
ClamAV update process started at Tue Feb 4 11:31:22 2014
Using IPv6 aware code
Querying current.cvd.clamav.net
TTL: 1694
Software version from DNS: 0.98.1
Retrieving http://database.clamav.net/main.cvd
Trying to download http://database.clamav.net/main.cvd (IP: 81.91.100.173)
Downloading main.cvd [100%]
Loading signatures from main.cvd
Properly loaded 2424225 signatures from new main.cvd
main.cvd updated (version: 55, sigs: 2424225, f-level: 60, builder: neo)
Querying main.55.76.1.0.515B64AD.ping.clamav.net
...
Next we'll need to create a clamd.conf
# /usr/local/etc/clamd.conf
LocalSocket /usr/local/var/run/clamav/clamd.sock
You'll need to ensure that the socket directory exists
$ mkdir /usr/local/var/run/clamav
You should now be able to run
$ clamd
to start the process.