Be without post after First in Biochemistry? It's a crime! (9)
I believe the answer is:
blackmail
'crime' is the definition.
(blackmail is a kind of crime)
'be without post' is the wordplay.
'be without' becomes 'black' (I can't justify this - if you can you should believe this answer much more).
'post' becomes 'mail' ('mail' can be a synonym of 'post').
'black'+'mail'='BLACKMAIL'
'after first in biochemistry? it's a' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for blackmail that I've seen before include "Crime of demanding money by threat of exposure" , "Extort illegally" , "Crime of demanding money to keep something secret" , "Lack a limb to execute this crime" , "Threaten" .)