No, I don't think that which you are describing can be defined as tinnitus. As you may well know, tinnitus is best defined as an acoustic-like sensation generated somewhere in the human body. Objective tinnitus can be heard by the patient and by the examiner. It may be caused by spasms-like movement of the small bones in the middle ear, spontaneous movement of the soft palate and sometimes by sounds generated in the cochlea (where the hearing nerves are located.) Subjective tinnitus is best defined as an acoustic-like sensation that is heard only by the patient and not by anyone else. Its cause lies somewhere in the auditory system.
In either case, tinnitus tends to be persistent. In your case, what you are experiencing is not persistent but exists only when you are walking. It is my guess that the clicking sound may be the result of what is referred to as a seismic effect. That is, walking itself produces a jarring motion that may create movement of the small bones or contractions muscles in the middle ear.
In order to test this hypothesis, consider doing the following: I) Walk slowly (with minimal jarring) and determine if the clicking sensation is present. 2) Then walk at your normal pace and determine if the clicking returns. 3) Move head up and down slowly and notice if the clicking is absent or present. 4). Then, vigorously, move your head up and down and determine if the clicking sound returns.
Another suggestion is to do the following: If you use hearing aids, take them off and then walk a brief distance and see if the clicking occurs. Put them on and follow the same procedure. If there is no clicking when the hearing aids are not worn, and it is present when they are, it is quite possible that the seismic effect is causing the problem.
At any rate, what you are describing does not appear to be a harbinger of something that should be of great concern. However, if it is a constant concern, by all means consult an ear specialist.
A word of caution: Regardless of the cause of the perceived sound, even though it is benign, constant, negative attention to that sound can create emotional disturbance. If a medical examination finds no evidence of a physical or medical problem, then be assured the clicking sound offers no threat to the quality of life.