As a rule, has army commander’s regular ploy (9)
I believe the answer is:
generally
'as a rule' is the definition.
('as a rule' means generally or typically)
'army commander's regular ploy' is the wordplay.
'army commander' becomes 'general' (I've seen this in another clue).
'regular' indicates alternate letters.
The alternating letters of 'ploy' are 'ly'.
'general'+'ly'='GENERALLY'
'has' acts as a link.
(Other definitions for generally that I've seen before include "For the most part" , "most of the time" , "In most cases, usually" , "In most cases, as a general rule" , "as usual" .)