Bill received in connection with port (4)
I believe the answer is:
acre
'port' is the definition.
(I've seen this before)
'bill received in connection with' is the wordplay.
I cannot really see how this works, but
'bill' could be 'ac' (abbreviation for account) and 'ac' is located in the answer.
'in connection with' could be 're' (regarding) and 're' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for acre that I've seen before include "Square measure of land" , "Middle East port" , "Unit of land area" , "region of ground" , "Mediterranean port" .)