Possibly buries discoloured tissue (6)
I believe the answer is:
bruise
'discoloured tissue' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'possibly buries' is the wordplay.
'possibly' indicates anagramming the letters.
'buries' anagrammed gives 'BRUISE'.
Can you help me to learn more?
(Other definitions for bruise that I've seen before include "Mark left by blow" , "Contusion" , "Injure underlying soft tissue or bone" , "Sign of injury" , "Skin injury" .)