Come again about dog (5)
I believe the answer is:
recur
'come again' is the definition.
(I've seen this before)
'about dog' is the wordplay.
'about' becomes 're' (regarding).
'dog' becomes 'cur' (a cur is an aggressive or scruffy dog).
'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" .)