One minute - it's not a land measure (3,4)
I believe the answer is:
sea mile
'measure' is the definition.
(I know that sea mile is a type of nautical linear unit)
'one minute it's not a land' is the wordplay.
I cannot really understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
'minute' could be 'm' (abbreviation) and 'm' is located in the answer.
'a' is found in the answer.
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sea mile that I've seen before include "unit of distance" , "Nautical distance" .)