org-clock-clocked-in-display

org-clock-clocked-in-display is a variable defined in `org-clock.el'.
Its value is

mode-line

Documentation:
When clocked in for a task, org-mode can display the current
task and accumulated time in the mode line and/or frame title.
Allowed values are:

both displays in both mode line and frame title
mode-line displays only in mode line (default)
frame-title displays only in frame title
nil current clock is not displayed

You can customize this variable.