Brains behind putting curbs on motorway in Maryland (10)
I believe the answer is:
mastermind
'brains' is the definition.
(I've seen this in another clue)
'behind putting curbs on motorway in maryland' is the wordplay.
'behind putting curbs' becomes 'astern' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'on' indicates putting letters inside (as in clothing 'on' a person).
'motorway' becomes 'MI' (resembles Ma, English motorway).
'in' is an insertion indicator.
'maryland' becomes 'MD' (abbreviation).
'astern' placed around 'mi' is 'astermin'.
'astermin' put within 'md' is 'MASTERMIND'.
Can you help me to learn more?
(Other definitions for mastermind that I've seen before include "Be behind" , "Planning supremo" , "Ringleader" , "Brainy TV quiz" , "Knowledge-testing TV quiz" .)