A new face: Sir Keir and State both on the up (6)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

A reversal (both on the up’ in a down light) of PM (hot off the press: ‘Sir Keir’ Starmer has been Prime Minister for all of five days) plus AVER (‘state’). ‘Both’ might suggest that the order of the particles is reversed – a reversal of ‘Sir Keir’ followed by a reversal of ‘state’ – but that is not what is required here.