Cloning in biology is the process of artificially creating an organism that is genetically identical to that of its original counterpart.
Cloning in the Buzz Lightyear of Star Command universe is an involved process - clones take time to grow (though they grow faster than normal humans while in their incubation tubes). Once outside the tubes, they grow at a normal rate.
In the episode "Clone Rangers", Zurg acquired DNA samples from Buzz, Mira and Booster in an attempt to create evil clone counterparts of them. However, due to his impatience, he ended up creating child versions of the three instead of the fully-matured clones he expected. Shortly after, he created another batch of clones whom he left in the incubation tubes for weeks: they emerged as extremely elderly versions of the team.