I think the term may be "re-up"
re-up?
fort
The noun phrase 'four week vacation' does not need to be hyphenated.
A four letter word meaning not kosher is: tref
Unit
Army
kill
aver
into
The word pine can have that meaning.
A four-letter word for cooking fat is "lard".
A four letter word meaning to grow light as the sun rises is dawn.