Act strangely by a fellow doctor’s burial place (8)
I believe the answer is:
catacomb
'burial place' is the definition.
(I've seen this before)
'act strangely by a fellow doctor's' is the wordplay.
'strangely' is an anagram indicator.
'by' is a charade indicator (letters next to each other).
'fellow' becomes 'co' (eg a co-worker is a fellow worker).
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'act' is an anagram of 'cat'.
'cat'+'a'+'co'+'mb'='CATACOMB'
(Other definitions for catacomb that I've seen before include "underground tunnels" , "Underground network" , "It's a grave situation" , "Burial-place" , "burial site" .)