She and I left to fly out (5)

I believe the answer is:

filly

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'she' is the definition.
Both the answer and definition are singular nouns.
Perhaps they are linked in a way I don't understand?

'i left to fly out' is the wordplay.
'left' becomes 'l' (common abbreviation).
'to' is a charade indicator (letters next to each other).
'out' indicates putting letters inside.
'i'+'l'='il'
'il' put into 'fly' is 'FILLY'.

'and' is the link.

Can you help me to learn more?

(Other definitions for filly that I've seen before include "Young mare" , "Young female horse" , "Female horse under four years old" .)

I've seen this clue in the Evening Standard.

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