Using that definition, you can call crossdressing "a hobby" because some crossdressers do it for pleasure, others for relaxation, some do it for both reasons, and most do it in their spare time.
Ham radio is my hobby, crossdressing is not.
I do not crossdress. I femulate, that is, I emulate a female.
Emulate means "to strive to equal or excel," according to Merriam-Webster's Online Dictionary.
I do not femulate in my spare time; I femulate all the time. Whether I am dressed in male or female garb, my heart, mind and soul are femulating.
And so it goes