Pirate well-trained behind bar, collecting empties primarily (11)
I believe the answer is:
counterfeit
'pirate well-trained behind' is the definition.
'counterfeit' can be an answer for 'pirate' (I've seen this before). I am unsure of the 'well-trained behind' bit.
'bar collecting empties primarily' is the wordplay.
'bar' becomes 'counter' (as in the counter of a pub or bar).
'collecting empties primarily' becomes 'feit' (I am not sure about this - if you are sure you should believe this answer much more).
'counter'+'feit'='COUNTERFEIT'
Can you help me to learn more?
(Other definitions for counterfeit that I've seen before include "Sham, fake" , "Forgery" , "copy" , "Pirate" , "Pretended, sham" .)