Youth doesn't start growing a lot (8)

I believe the answer is:

tripling

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'growing a lot' is the definition.
The definition and answer can be both related to change as well as being present participle verbs.
Perhaps they are linked in a way I don't understand?

'youth doesn't start' is the wordplay.
'youth' becomes 'stripling' (I've seen this before).
'doesn't start' means to remove the first letter.
'stripling' with its initial letter taken away is 'TRIPLING'.

Can you help me to learn more?

(Another definition for tripling that I've seen is " Increasing threefold".)

I've seen this clue in The Guardian.

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