Scouse entertainer vacillates somewhat (5)

I believe the answer is:

cilla

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

'scouse' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'entertainer vacillates somewhat' is the wordplay.
'somewhat' indicates the answer is hidden within the clue.
'CILLA' is hidden within 'entertainer vacillates'.

Can you help me to learn more?

(Other definitions for cilla that I've seen before include "Colourful old singer" , "- Black, TV personality and singer" .)

I've seen this clue in The Sun.

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