On keyclone simply hit the Pause key on your keyboard, or rebind the Pause function in the settings to something to toggle passing on/off

I like KSBoxer's solution to it though...the Cairne Zerg has ranks set up so that the Main/Lead char can guildchat, and all the alts are Disallowed Guild Chat rights; set all chars to /guildchat and talk on your main without ever having to worry about pausing/unpausing midcombat lol