Running out of pins in a 4x7-segment display clock
The basic idea is this:

First, connect segment A of each display together, and all the segment Bs together, and all the segment Cs and so on.  Each "group" is driven by one pin on the Arduino.  For this you will need seven pins.

Your displays will have either a common anode or common cathode - perhaps you have that connected straight to +5v or straight to ground currently.  Instead, you connect the "common" pin from each display to a spare pin on your Arduino - so using another four pins.

Remember the resistors too.

Now, you can light up any segment on any display, by setting the appropriate segment pin and the appropriate common pin to the right values.

Make sense?