Green leader upset about motorway (7)
I believe the answer is:
emerald
'green' is the definition.
(I know that emerald is a type of green)
'leader upset about motorway' is the wordplay.
'upset' indicates anagramming the letters.
'about' means one lot of letters goes inside another.
'motorway' becomes 'M' (as in motorway names - M1, M4 etc).
'leader' with letters rearranged gives 'eerald'.
'eerald' placed around 'm' is 'EMERALD'.
(Other definitions for emerald that I've seen before include "Green variety of beryl" , "Mere lad (anag.)" , "On of the Greens" , "Green - jewel" , "Ireland is often called The .......Isle" .)