Leader's shot carrying Muirfield's first green (7)
I believe the answer is:
emerald
'green' is the definition.
(emerald is a shade of green)
'leader's shot carrying muirfield's first' is the wordplay.
'shot' indicates anagramming the letters.
'carrying' is an insertion indicator.
'muirfield's first' becomes 'm' (1st letter of 'muirfield').
'leader' with letters rearranged gives 'eerald'.
'eerald' enclosing 'm' is 'EMERALD'.
(Other definitions for emerald that I've seen before include "Gem associated with Ireland" , "Green variety of beryl" , "Precious green stone" , "Ireland is often called The .......Isle" , "Led mare (anag.)" .)