Code:
alias clearcnicks {
  var %i = $cnick(0)
  while %i {
    if $cnick(%i) && $ifmatch != $!me { cnick -r $cnick(%i) }
    dec %i
  }
}

Prefix the 'cnick' with a period (" .cnick -r $cnick(%i) ") to hide the * Removed xxx from color list