Word of caution: of course OCCT is a low profile program and noone sane would target it. But there has been a lot of "supply chain" attacks lately, where legitimate applications and frameworks ( and ironically even security software like Solarwinds) get hacked on source level and bad update with trojans is pushed to unsuspecting clients.
My recommendation - simply wait for next release of OCCT, devs are probably aware of triggering the Windows Defender and will push new app build soon.
EDIT: actually the update is up already, in changelog for OCCT:
Changelog
OCCT 8.1.1
Main
Small update to avoid a false positive detection in Microsoft's antivirus