This measure confused with the equivalent of hectare (4)
I believe the answer is:
acre
'this measure confused with the equivalent of hectare' is the definition.
'acre' can be an answer for 'measure' (acre is a kind of measure). I'm not certain of the remainder of the definition.
'this measure confused with' is the wordplay.
'this measure' becomes 'A' (A is an example).
'confused with' becomes 'cre' (I can't explain this - if you can you should believe this answer much more).
'a'+'cre'='ACRE'
Can you help me to learn more?
(Other definitions for acre that I've seen before include "Unit of land area" , "Middle East port" , "Mediterranean port" , "Area measure - Israeli port - Brazilian state" , "Old unit of area - old port" .)