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

I believe the answer is:

whistle

I'm a little stuck... Click here to teach me more about this clue!

'suit in the east end' is the definition.
'whistle' can be an answer for 'suit' (I've seen this before). I am unsure of the 'in the east end' bit.

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for whistle that I've seen before include "sound surprised" , "He wilts (anag.)" , "Pucker up and blow" , "L.S.White (anag.)" , "Shrill piping sound" .)

I've seen this clue in The Independent.

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