Direct route to Alabama (6)
I believe the answer is:
lineal
'direct' is the definition.
('lineal' can be a synonym of 'direct')
'route to alabama' is the wordplay.
'route' becomes 'line' (line is a kind of route).
'to alabama' becomes 'al'.
'line'+'al'='LINEAL'
(Other definitions for lineal that I've seen before include "In a straight row" , "Having only one dimension" , "One-dimensional" , "Transmitted by direct descent" , "In line of descendants" .)