It is ok to have gap in your work experience. Do not get on defensive to hide the gap. Be confident while answering this question. Your answer should not be that I did not find job for one year. Rather you can turn this gap into an opportunity to showcase your attitude towards spending time to learn things.
Sample answer is:
I have worked for 3 years in Software industry. I have family emergency for which I have to spend time to take care of my family matters. Due to which I took time off from work for 6 months. Though I was not working during this time, I utilized this time to grow my knowledge. I attended online courses on Cloud Computing to learn the new technologies in this area.