Strong booze in pack partly emptied (7)
I believe the answer is:
scrumpy
'strong booze' is the definition.
The definition suggests a singular noun which matches the answer.
'pack partly emptied' is the wordplay.
'pack' becomes 'scrum' (I can't explain this - if you can you should give a lot more credence to this answer).
'emptied' says to hollow out the word (remove centre letters).
'partly' with its middle taken out is 'py'.
'scrum'+'py'='SCRUMPY'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for scrumpy that I've seen before include "Strong or dry cider" , "Strong English cider" , "rough drink" , "Rough strong cider" , "Strong drink" .)