Crossword Genius

What she lost in broad British estuary (3,4)

Ross

I believe the answer is:

the wash

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

'broad british estuary' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'what she lost' is the wordplay.
'lost' indicates anagramming the letters.
'what'+'she'='whatshe'
'whatshe' is an anagram of 'THE WASH'.

'in' acts as a link.

Can you help me to learn more?

(Another definition for the wash that I've seen is " bay".)

I've seen this clue in The Telegraph.
Want a hint initially instead of a full solution? Install my app