Completely confused (3,2,3)
I believe the answer is:
all at sea
'completely confused' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for all at sea that I've seen before include "state of confusion" , "Rescuers at Dunkirk were thus" , "Entire crew" , "Is a sailor's life so" , "Completely confused - in a boat?" .)