Gives megastar champagne discreetly by way of a stiffener (6)
I believe the answer is:
starch
'a stiffener' is the definition.
(starch is used to make fabric stiff)
'gives megastar champagne discreetly by way' is the wordplay.
'STARCH' is hidden within the letters.
However, I'm uncertain how the hidden word is indicated.
'of' is the link.
Can you help me to learn more?
(Other definitions for starch that I've seen before include "Stiffness of manner" , "Reserve" , "Setter" , "Substance found mainly in potatoes and cereals" , "rigid" .)