Copper left post, admitting booze primarily to blame (8)
I believe the answer is:
culpable
'to blame' is the definition.
(thesaurus)
'copper left post admitting booze primarily' is the wordplay.
I cannot really see how this works, but
'copper' could be 'cu' (chemical symbol) and 'cu' is found within the answer.
'left' could be 'l' (common abbreviation) and 'l' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for culpable that I've seen before include "Guilty" , "Criminally responsible" , "Blameworthy, censurable" , "Answerable" , "Proboscis" .)