Son drunk back to mix salad (4)
I believe the answer is:
toss
'mix salad' is the definition.
(I've seen this in another clue)
'son drunk back' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'drunk' becomes 'sot' (both can mean someone who drinks too much).
'back' says the letters should be written backwards.
's'+'sot'='ssot'
'ssot' in reverse letter order is 'TOSS'.
'to' acts as a link.
(Other definitions for toss that I've seen before include "Heads or tails throw" , "Throw (coin or caber)" , "Fall from horse" , "cast" , "Throw (coin) so as to choose" .)