Small dog’s head, black (5)
I believe the answer is:
dinky
'small' is the definition.
('dinky' can be similar in meaning to 'small')
'dog's head black' is the wordplay.
'head' says to take the initial letters.
'black' becomes 'inky' ('inky' can be similar in meaning to 'black').
The first letter of 'dogs' is 'd'.
'd'+'inky'='DINKY'
(Other definitions for dinky that I've seen before include "Neat and dainty" , "Dainty (colloq.)" , "Attractively small" , "Small, neat and cute" .)