Gave off energy, keeping Anne's successor in pain (8)

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

anagram of GAVE, then E(energy) containing GRI(George Rex Imperator – King George I, successor to Queen Anne). Got this from the definition and worked out the wordplay for the blog. There’s comments that this should be GR and I separately, apologies to my long gone namesake king.