Metal layer on top gets reddish brown colour (5)
I believe the answer is:
henna
'reddish brown colour' is the definition.
'henna' can be an answer for 'colour' (I have seen 'Local colour' mean 'henna' so perhaps 'colour' could also mean 'henna'). I am not certain of the 'reddish brown' bit.
'metal layer on top' is the wordplay.
'metal' becomes 'na' (Na is an example).
'layer' becomes 'hen' (animal which lays eggs).
'on top' says to put letters next to each other (in a down clue, some letters go above others).
'na' put after 'hen' is 'HENNA'.
'gets' acts as a link.
Can you help me to learn more?
(Other definitions for henna that I've seen before include "A shrub, its red dye" , "Reddish-brown plant dye" , "Red-brown plant dye" , "Pigment used on skin" , "Dye used in skin decoration" .)