Gains more favour as it becomes ever bigger (5,2)

I believe the answer is:

grows on

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

'gains more favour as it' is the definition.
I don't know anything about this answer so I can't tell whether this works.

'becomes ever bigger' is the wordplay.
I cannot really understand how this works, but
'becomes' could be 'grows' (I've seen this in another clue) and 'grows' is found within the answer.
The remaining letters 'on' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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