Invest in road building (6)
I believe the answer is:
ordain
'invest' is the definition.
(I know that invest is the is a more specific form of the action of ordain.)
'in road building' is the wordplay.
'building' indicates anagramming the letters.
'in'+'road'='inroad'
'inroad' with letters rearranged gives 'ORDAIN'.
(Other definitions for ordain that I've seen before include "Invest with ministerial authority" , "Inroad (anag.)" , "Rule" , "Make a decree" , "Install as priest" .)