Lose energy - on the bottle (6)
I believe the answer is:
flagon
'bottle' is the definition.
(I've seen this before)
'lose energy on' is the wordplay.
'lose energy' becomes 'flag' (I've seen this in another clue).
'flag'+'on'='FLAGON'
'the' acts as a link.
(Other definitions for flagon that I've seen before include "Large wine vessel" , "Large container for serving drink" , "Wine jug" , "Large wine-bottle, jug" , "Large drinks container" .)