Murderer concealing first of bodies in shack (5)
I believe the answer is:
cabin
'shack' is the definition.
(thesaurus)
'murderer concealing first of bodies' is the wordplay.
'murderer' becomes 'cain' (Cain who killed Abel).
'concealing' means one lot of letters goes inside another.
'first of' says to take the initial letters.
The initial letter of 'bodies' is 'b'.
'cain' placed around 'b' is 'CABIN'.
'in' is the link.
(Other definitions for cabin that I've seen before include "Hamper" , "Railway signal box" , "Small room on a ship" , "Wooden shack" , "Small room or hut" .)