Completely finished covering the whole thing (3,4)
I believe the answer is:
all over
'completely finished' is the definition.
'covering the whole thing' is the wordplay.
I cannot really see how this works, but
'covering' could be 'over' (I've seen this in another clue) and 'over' is present in the answer.
'whole' could be 'all' (I've seen this in another clue) and 'all' is located in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for all over that I've seen before include "typically" , "Obsessed with" , "covering everything" , "Everywhere (bar the shouting?)" , "Excessively attentive" .)