Adolescent growth, terrible mistake (8)

I believe the answer is:

bumfluff

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'adolescent growth' is the definition.

'terrible mistake' is the wordplay.
'terrible' becomes 'bum' (I can't justify this - if you can you should give a lot more credence to this answer).
'mistake' becomes 'fluff' (fluff is a kind of mistake).
'bum'+'fluff'='BUMFLUFF'

Can you help me to learn more?

I've seen this clue in The Guardian.

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