Frowning, one of Fab Four heard brother was in debt (6-6)

I believe the answer is:

beetle-browed

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

'frowning one of fab four' is the definition.
'beetle-browed' can be an answer for 'frowning' (thesaurus). I'm unsure of the 'one of fab four' bit.

'heard brother was in debt' is the wordplay.
'heard' becomes 'beetle' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'brother' becomes 'br'.
'was in debt' becomes 'owed' (I've seen this before).
'beetle'+'br'+'owed'='BEETLE-BROWED'

Can you help me to learn more?

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app