Scot's exclamation about colour (5)
I believe the answer is:
ochre
'colour' is the definition.
(I know that ochre is a colour)
'scot's exclamation about' is the wordplay.
'scot's exclamation' becomes 'och' (I've seen this in another clue).
'about' becomes 're' (regarding).
'och'+'re'='OCHRE'
(Other definitions for ochre that I've seen before include "natural colouring" , "Money" , "Yellow-orange colour" , "Earthy pigment - light brownish-yellow" , "Light yellow-brown colour" .)