Gilbert? It’s Gilbert heading off distressed over carpet ultimately (10)

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

*(IT’S + <g> ILBERT ) + <carpe> T ; “heading off” means first letter is dropped from anagram, indicated by “distressed”; “ultimately” means last letter only; the reference is to librettist Sir William Gilbert (1836-1911), half of the musical partnership Gilbert and Sullivan