Sweet but posh bloke with bearing and energy (6)
I believe the answer is:
toffee
'sweet' is the definition.
(toffee is a kind of sweet)
'posh bloke with bearing and energy' is the wordplay.
'posh bloke' becomes 'toff' (informal term for an upper class person).
'with' is a charade indicator (letters next to each other).
'bearing' becomes 'e'.
'and' is a charade indicator (letters next to each other).
'energy' becomes 'e' (physics symbol as in E=mc2).
'toff'+'e'+'e'='TOFFEE'
'but' acts as a link.
(Other definitions for toffee that I've seen before include "Chewy sweet" , "Chewy confectionery" , "Sweet made with heated butter and sugar" , "sticky stuff" , "Sugar/butter sweet" .)