Boozer turned on initially amenable canine (4)
I believe the answer is:
tosa
'canine' is the definition.
(Japanese breed of dog)
'boozer turned on initially amenable' is the wordplay.
'boozer' becomes 'sot' (I've seen this in other clues).
'turned' shows that the letters should be reversed in order.
'on' says to put letters next to each other.
'initially' indicates taking the first letters.
The initial letter of 'amenable' is 'a'.
'sot' reversed gives 'tos'.
'tos'+'a'='TOSA'
(Other definitions for tosa that I've seen before include "Fierce Japanese dog breed" , "heavily built dog" , "Dog of Japanese origin" , "Japanese fighting dog" , "5 [MANS BEST FRIEND]" .)