Erstwhile queen lost crumpled suit in the East End (7)

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

Erstwhile queen lost crumpled suit in the East End *(<er> STWHILE ); “ queen (=ER, for Elizabeth Regina) lost” means letters “er” are dropped from anagram, indicated by “crumpled”; a whistle and flute is Cockney rhyming slang for a suit!