Good blocks hammered into cross (5)
I believe the answer is:
tigon
'cross' is the definition.
(offspring of a lion and a tiger)
'good blocks hammered into' is the wordplay.
'good' becomes 'g' (abbreviation).
'blocks' is an insertion indicator (upper walls off glass inside formal).
'hammered' indicates anagramming the letters (slang term for drunk).
'into' with letters rearranged gives 'tion'.
'g' inserted within 'tion' is 'TIGON'.
(Other definitions for tigon that I've seen before include "Hybrid offspring of two big cats" , "Cross between two big cats" , "cat cross" , "Big hybrid of the cat family" , "Animal" .)