Ghost essentially taking oddly vacated seat in feast? (6)

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

BANQU [et] (feast), with the middle letter (essentially) of [gh] O [st] replacing ET, which we get by removing the odd-numbered letters (oddly vacated . . .) of [s]E[a]T. Clue-as-definition: in the play, Banquo’s ghost appears to sit in Macbeth’s seat during a feast.