Something invigorating filling panto nicely (5)

I believe the answer is:

tonic

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

'something invigorating' is the definition.
(I've seen this in another clue)

'filling panto nicely' is the wordplay.
'TONIC' is hidden in amongst the letters.
However, I'm unsure how this is indicated.

Can you help me to learn more?

(Other definitions for tonic that I've seen before include "fizz" , "that may be mixed with gin" , "Medical restorative" , "Producing tension of muscles" , "A pick-me-up drink, nice with gin" .)

I've seen this clue in The Times.

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.