Crossword Genius

Sorry a girl’s lost, that is (3)

Ross

I believe the answer is:

sad

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

'sorry a girl's lost that is' is the definition.
'sad' can be an answer for 'sorry' (I've seen this before). I'm unsure of the rest of the definition.

'sorry a girl's lost that is' is the wordplay.
'sorry' becomes 'sa' (I can't explain this - if you can you should give a lot more credence to this answer).
'a girl's' becomes 'dis'.
'lost' is a deletion indicator.
'that is' becomes 'is'.
'dis' with 'is' removed is 'd'.
'sa'+'d'='SAD'

Can you help me to learn more?

(Other definitions for sad that I've seen before include "grey" , "Despondent" , "Dejected" , "Deplorable" , "Doleful" .)

I've seen this clue in the Evening Standard.
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