American drunkard turns to fighting dog (4)
I believe the answer is:
tosa
'fighting dog' is the definition.
'tosa' can be an answer for 'dog' (I have seen 'Big dog' mean 'tosa' so perhaps 'dog' could also mean 'tosa'). I'm not certain of the 'fighting' bit.
'american drunkard turns' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'drunkard' becomes 'sot' (sot can mean a drunken person).
'turns' is a reversal indicator.
'a'+'sot'='asot'
'asot' reversed gives 'TOSA'.
'to' is the link.
Can you help me to learn more?
(Other definitions for tosa that I've seen before include "Dog of Japanese origin" , "Fierce Japanese dog breed" , "Japanese fighting dog" , "heavily built dog" , "Big dog" .)