Dog Communist compiler (3,6)
I believe the answer is:
red setter
'dog' is the definition.
(red setter is a kind of dog)
'communist compiler' is the wordplay.
'communist' becomes 'red' (red can informally mean communist).
'compiler' becomes 'setter' (both can mean a writer of crosswords).
'red'+'setter'='RED SETTER'
(Other definitions for red setter that I've seen before include "supplier of crosswords to the Daily Worker?" , "One of my best friends" , "Gun dog" , "one identifying the game" , "Shepherds are delighted to see this" .)