This one driving me mad! I have for 14d Terreplein, but it is not an eastern fortification - please explain to this dimwit - of course could be wrong answer entirely! Yet does fit with Thebes and Lido??
Interloper with nothing to lose ..Lose the O (nothing) Running wild (indicates an anagram ) round E (eastern) makes Terreplein (fortification ) a rampart where guns are mounted.