Reappear concerning dog (5)
I believe the answer is:
recur
'reappear' is the definition.
(thesaurus)
'concerning dog' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'dog' becomes 'cur' (both can mean a despicable person).
're'+'cur'='RECUR'
(Other definitions for recur that I've seen before include "Happen repeatedly" , "Come round again" , "Be repeated" , "expected to return" , "Persist" .)