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.
'left' becomes 'port' (left side of a ship - opposite of starboard).
'take' says to put letters next to each other.
'over' becomes 'on' (physically on top of).
'port'+'i'+'on'='PORTION'
(Other definitions for portion that I've seen before include "Share, helping" , "Part of a whole" , "Amount of food" , "Serving" , "allotment" .)