Stop drinking broth laced with beer if short of energy (5,2)
I believe the answer is:
sober up
'stop drinking' is the definition.
(to sober up is to stop drinking)
'broth laced with beer if short of energy' is the wordplay.
'broth' becomes 'soup' (I've seen this before).
'laced with' means one lot of letters goes inside another (I've seen this in other clues).
'if short of' indicates named letters should be taken away.
'energy' becomes 'e' (physics symbol as in E=mc2).
'beer' with 'e' taken out is 'ber'.
'soup' going around 'ber' is 'SOBER UP'.
(Other definitions for sober up that I've seen before include "Get real" , "What you do when drink wears off" , "become serious" , "Become less drunk" .)