Energy beginning to soar, keep going without finishing coffee (8)
I believe the answer is:
espresso
'coffee' is the definition.
(espresso is a kind of coffee)
'energy beginning to soar keep going without finishing' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mc2).
'beginning to' indicates taking the first letters.
'keep going' becomes 'presson' (I've seen this before).
'without finishing' means to remove the last letter.
The first letter of 'soar' is 's'.
'presson' with its final letter taken off is 'presso'.
'e'+'s'+'presso'='ESPRESSO'
(Other definitions for espresso that I've seen before include "Type of coffee" , "Kind of coffee made with steam" , "strong drink" , "Coffee drink" , "Strong black coffee" .)