oompa - everything as will 37 says ... the fourth letter of 'calls for attention' is an alternative ... usually would be 3 letters without this included ... If this helps
Remarkably, despite all your help, I still cannot fill the blank. I must have letters 1, 5&6 correct from the theme, and letters 2&3 come from write-ins, and yet I still don’t get it. 1 damned letter!
Oompa, given you are relatively new to the Listener, do yourself a favor (yes I'm American) and get the Chambers app. But for the clue that is confounding you, the 4th and 5th letters are from "Silence!" as a command. Not "sh" but ...