State without a highway? Not entirely (4)
I believe the answer is:
utah
'state' is the definition.
(Utah is a US state)
'without a highway? not entirely' is the wordplay.
'not entirely' indicates the answer is hidden within the clue.
'UTAH' can be found hidden inside 'without a highway'.
(Other definitions for utah that I've seen before include "member of union" , "The American Mormon state" , "Bryce Canyon US state" , "American state associated with Mormons and their faith" , "Mormons are found here in a hut" .)