Clipping planes are invisible planes that NX creates by default, in front of and behind the model.These planes are at a default distance where the model does not intersect them when you rotate it.
FCD - Front Clipping Distance
BCD - Back Clipping Distance
Menu > View > Camera > Edit
You can enter desired values manually for FCD and BCD
I checked this in NX 9, when this command is started, Clipping section has some default values for 'Front Clipping Distance' and 'Back Clipping Distance'. Then I had defined expressions for FCD,BCD and tried to use them, but seems that it is not possible to use expressions for clipping values. However, if I enter the expression name and press tab, it takes the value of expression as shown. Same behaviour in NX 10.