Heard a girl cry (4)

I believe the answer is:

alas

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

'heard' is the definition.
The answer and definition are not the same part of speech.

'a girl cry' is the wordplay.
'girl' becomes 'lass' (lass can informally mean a girl).
'cry' shows a homophone (sound like) (cried aloud).
'lass' sounds like 'las'.
'a'+'las'='ALAS'

Can you help me to learn more?

(Other definitions for alas that I've seen before include "woebegone expression" , "Cry of grief" , "Unhappily" , "Sadly, unfortunately" , "Too bad, so sad" .)

I've seen this clue in The Mirror.

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