Hunk's small short dog (4)
I believe the answer is:
slab
'hunk's' is the definition.
(I've seen this before)
'small short dog' is the wordplay.
'short' says to take the initial letters.
'dog' becomes 'lab' (short for labrador**).
The initial letter of 'small' is 's'.
's'+'lab'='SLAB'
(Other definitions for slab that I've seen before include "Chunk of wood" , "Broad, thick piece of wood, stone" , "Thick piece of something" , "Flat piece of stone or 20" , "Piece of paving" .)