Drink nothing when back for work (4)
I believe the answer is:
opus
'for work' is the definition.
(an opus is an artistic work)
'drink nothing when back' is the wordplay.
'drink' becomes 'sup' (to sup is to drink).
'nothing when' becomes 'o' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'back' is a reversal indicator.
'sup'+'o'='supo'
'supo' backwards is 'OPUS'.
Can you help me to learn more?
(Other definitions for opus that I've seen before include "Work (mus.)" , "Composer's work" , "Work (of a composer?)" , "A Latin work" , "Composition - magnum __" .)