To be honest when someone asks me about clinical governance I go completely blank. Personally I think no one knows exactly what it means but can only describe what they think it means. The word is to open for interpretation and therefor to my opinion not well chosen.
For this reason I think you better return the question to the interviewer with the comment that you cannot answer the question because no clear definition (not well defined, no exact borders) can be given and you might misinterprete his question. Then you give some examples like it has to do with CPD, buddy system, EBP and so on. After this you ask the interviewer if he or she is able to define for you clinical governance so you are able to answer his/her question instead of doing some guess work about the meaning of the word.
It is just fashion unfortunately we have to deal with it. To my opinion the same with p.e. Evidence based practice, unfortunately there is very little clinical evidence to physiotherapy treatment and a lot of evidence which is used is to my opinion just "what someone has thought and spinned a theory around it" Just think p.e. manipulations done by a chiropractor or a manual therapy trained physio; they might do the same but their theory (and therefor thinking what happens) is different.
IN this way you have to look at clinical governance, try to return the question in a polite way because if you are unable to put borders on the question every answer will be wrong!
Good luck for the future, I think you deserve it.