Concoction knocked back during power breakfast (4)
I believe the answer is:
brew
'concoction' is the definition.
(thesaurus)
'knocked back during power breakfast' is the wordplay.
'knocked back' is a reversal indicator.
'during' indicates a hidden word.
'werb' can be found hidden inside 'power breakfast'.
'werb' reversed gives 'BREW'.
(Other definitions for brew that I've seen before include "Infusion" , "A pot of tea?" , "Cup of tea (informal)" , "Make (tea/coffee)" , "Plot" .)