Bear short of energy (7)
I believe the answer is:
undergo
'bear' is the definition.
(undergoing is a kind of bearing)
'short of energy' is the wordplay.
'short of' becomes 'under' (eg short of 10 means under 10).
'energy' becomes 'go' (go can mean energy or enthusiasm).
'under'+'go'='UNDERGO'
(Other definitions for undergo that I've seen before include "Endure, experience something" , "experience needed" , "Experience or live through" , "put up with" , "Withstand" .)