Army officer is common (7)
I believe the answer is:
general
I believe this is a double definition.
'army officer' is the first definition.
(type of army officer)
'common' is the second definition.
(I've seen this before)
'is' acts as a link.
(Other definitions for general that I've seen before include "High-ranking officer" , "High ranking officer" , "top brass" , "Of wide application" , "Officer of the highest rank" .)