A red bed, sadly covered in hair (7)
I believe the answer is:
bearded
'covered in hair' is the definition.
The answer and definition can be both to do with fundamental existence as well as being past participle verbs.
Perhaps they are linked in a way I don't understand?
'a red bed sadly' is the wordplay.
'sadly' indicates an anagram.
'a'+'red'+'bed'='aredbed'
'aredbed' is an anagram of 'BEARDED'.
Can you help me to learn more?
(Another definition for bearded that I've seen is " With hirsute chin".)