The bit left, I take over (7)
I believe the answer is:
portion
'the bit' is the definition.
(thesaurus)
'left i take over' is the wordplay.
I cannot really see how this works, but
'left' could be 'port' (left side of a ship - opposite of starboard) and 'port' is present in the answer.
'i' is within the answer.
'over' could be 'on' (physically on top of) and 'on' is present in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for portion that I've seen before include "Share, helping" , "Part of a whole" , "Amount of food" , "Serving" , "allotment" .)