Is a destination airport necessary for cross-country VFR departure clearance?
Just say direction of flight.

If they need more info, they'll ask:


  N12345: Say destination.


I've almost never heard that, except if they think you might be headed towards weather or a TFR.

Examples:


  Understand you're headed to the south.  Be aware of Stadium TFR in effect.


or


  Understand you're headed to the south; have had reports of severe weather in that direction.