As far as the doctor is concerned, it's a grave situation (4)
I believe the answer is:
tomb
'a grave situation' is the definition.
(where a grave may be situated)
'as far as the doctor' is the wordplay.
'as far as' becomes 'to'.
'the doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'to'+'mb'='TOMB'
'is concerned it's' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for tomb that I've seen before include "Burial-vault" , "Mausoleum" , "Catacomb" , "remains here" , "grave situation" .)