Type of nut (9)
(Other definitions for macadamia that I've seen before include "nut-tree" , "Australian tree with edible nuts - a CIA madam (anag)" , "Queensland nut" , "Nut-bearing tree" , "Am I a cad, ma? (anag) - Australian nut tree" .)
'type of nut' is the definition.
(I know that pecan is a type of edible nut)
This is all the clue.
(Other definitions for pecan that I've seen before include "of nuts" , "Nut tree of the southern United States and Mexico" , "US nut tree" , "Smooth pinkish-brown nut, nice in pie" , "Something like a walnut" .)