Only half studying insects book, put Six Feet down? (6)

I believe the answer is:
entomb
'put six feet down?' is the definition.
'entomb' can be an answer for 'put' (thesaurus). I'm not certain of the 'six feet down?' bit.
'only half studying insects book' is the wordplay.
'only half studying insects' becomes 'entom' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'book' becomes 'b' (abbreviation for book).
'entom'+'b'='ENTOMB'
Can you help me to learn more?
(Other definitions for entomb that I've seen before include "Place in a sepulchre" , "shut up patients?" , "put in ground" , "Incarcerate" , "Bury, place in a crypt" .)
