I always talk back by

saying: well, I guess everybody has his weakness, right?

Then say: my weakness is***, but I always do*** to improve.

Another thought: if your 5-year goal is to become***, and you are lack of this experience or skills, I can also mention this as your weakness and indicate you will improve.Am I right?

Bottom line: be open-minded to this kind of question.Don't try to hide from your weakness. If you have good experience and education, realizing your weakness is a good way to improve your skill. Let me put it this way. Be positive.