Terribly upset overturning drinks (5)
I believe the answer is:
sodas
'drinks' is the definition.
(soda is a kind of drink)
'terribly upset overturning' is the wordplay.
'terribly' becomes 'so' (I've seen this in other clues).
'upset' becomes 'sad' (I've seen this before).
'overturning' is a reversal indicator.
'sad' reversed gives 'das'.
'so'+'das'='SODAS'
(Other definitions for sodas that I've seen before include "Soft drinks" , "Fizzy drinks" .)