Depends on your overall circumstances, assuming normal working hours of your wife during the week (9-5, Mon-Fri). If you are planning a punt on a weekday, you can say you were called into office for an urgent meeting, which will last a few hours. On the weekend, likely to be more tricky as less viable excuses given the situation surrounding corona. Possible excuses given easing of lockdown restrictions, playing football with mates in the park, going to the pub with mates or going out shopping for items for yourself.
Also, your excuses depends on what kind of session you booking. Are you booking a WG that you can get to fairly quickly or quite a distance from you? how long are you looking to book? - a quick pump n dump or an 1-2Hrs? The shorter the time frame you will be out, your excuse maybe somewhat easier as going out for a short while is plausible during lockdown compared to a longer time frame.