Black for one short layer of coal (3)
I believe the answer is:
sea
'black for one' is the definition.
(as in the Black Sea)
'short layer of coal' is the wordplay.
'short' means to remove the last letter.
'layer of coal' becomes 'seam' (I've seen this in another clue).
'seam' with its last letter removed is 'SEA'.
(Other definitions for sea that I've seen before include "eg Dead, Red" , "Division of an ocean" , "Eg, Aral, Ross, Irish" , "Cause of flooding" , "The deep" .)