Acting with caution around Sicily’s Madam White (10)

I believe the answer is:
chardonnay
'white' is the definition.
(I've seen this before)
'acting with caution around sicily's madam' is the wordplay.
I cannot really understand how this works, but
'acting' could be 'on' (I've seen this in other clues) and 'on' is present in the answer.
'around' could be 'c' (abbreviation for 'circa') and 'c' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for chardonnay that I've seen before include "drink" , "White wine grape" , "Variety of white wine" .)
