Come again about dog (5)
I believe the answer is:
recur
'come again' is the definition.
(I've seen this in another clue)
'about dog' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'dog' becomes 'cur' (both can mean a despicable person).
're'+'cur'='RECUR'
(Other definitions for recur that I've seen before include "Happen again (5)" , "Persist" , "Be repeated" , "Happen again or repetitively" , "Return to mind" .)