Perform well in, increasing gradually in volume (8)

I believe the answer is:

swelling

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

'increasing gradually in volume' is the definition.
'swelling' can be an answer for 'volume' (thesaurus). I am not sure about the 'increasing gradually in' bit.

'perform well in' is the wordplay.
'perform' becomes 'sing' (to perform a song).
'in' means one lot of letters goes inside another.
'sing' placed around 'well' is 'SWELLING'.

Can you help me to learn more?

(Other definitions for swelling that I've seen before include "increasing in volume" , "Growth" , "area suffering inflation" , "Bulge" , "Lump" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.