You can find information about Jury service within the Staff Handbook
It states that if you are called for Jury Service / as a witness in court you should let your line manager know (who will inform People and Culture Team). We will give you time off to attend - you must claim loss of earnings through the court so we can adjust your salary accordingly.
It could be that you are not needed in court in the afternoon and so can come back to work for half a day. Please keep your line manager and People and Culture informed of when you do and don't work, and what you will be claiming as 'loss of earnings'.
There is some helpful information about what you can claim on the .gov website - https://www.gov.uk/jury-service/what-you-can-claim-if-youre-an-employee
The loss of earnings form (to be completed by staff member and Safe Families and Home for Good) can be found on here - https://www.gov.uk/government/publications/claim-a-loss-of-earnings-or-benefit-during-jury-service