Boozer: he's turned into a swine! (8)
I believe the answer is:
alehouse
'boozer' is the definition.
'he's turned into a swine' is the wordplay.
'turned' indicates anagramming the letters.
'into' means one lot of letters goes inside another.
'swine' becomes 'louse' (I can't explain this - if you can you should give a lot more credence to this answer).
'he' anagrammed gives 'eh'.
'a'+'louse'='alouse'
'eh' going inside 'alouse' is 'ALEHOUSE'.
Can you help me to learn more?
(Other definitions for alehouse that I've seen before include "Inn" , "Hostelry (of old)" , "the nineteenth?" , "drinks here?" , "old tavern" .)