This is a container clue - one word or phrase goes inside another word or phrase to form the answer.
Look for 'Egypt's last queen' (a famous historical figure) containing the letters that spell 'empire' with some letters removed. 'Sacked' indicates that letters should be taken away from 'empire'.
Answer: PERIMETER | Egypt's last queen is CLEOPATRA, but we only need PETER (P-E-T-E-R). 'Empire sacked' means remove some letters from EMPIRE, leaving RIM. PETER contains RIM to give PE(RIM)ETER = PERIMETER.