One suit makes a Scottish outfit (6)
I believe the answer is:
hearts
I believe this clue is a double definition.
'one suit' is the first definition.
(hearts is a playing card suit)
'a scottish outfit' is the second definition.
(Scottish football team Heart of Midlothian FC)
'makes' is the link.
(Other definitions for hearts that I've seen before include "They beat" , "Central parts" , "Suit in pack" , "Playing card suit" , "not clubs" .)