If you select the clothing and go to the surfaces tab, you can make it see through by reducing "cutout opacity". You shouldn't need anything any kind of addon.
not particularly you can use cutout opacity as is but that's not ideal.
see this post though (https://zonegfx.com/forums/topic/iray-fabric-translucent/page/2/#post-479698) for better instructions on semitransparent clothing, there are some additional methods and good ideas in the rest of the thread too.