In general a wise rule (3)
I believe the answer is:
law
'rule' is the definition.
(I know that rule can be written as law)
'in general a wise' is the wordplay.
'in' indicates the answer is hidden within the clue.
'LAW' can be found hidden inside 'general a wise'.
(Other definitions for law that I've seen before include "Rule, statute" , "'Possession is nine points of the ...'" , "Regulation" , "Edict" , "Official rule" .)