Top military officers thought of as bold? (5)
I believe the answer is:
brass
I believe this clue is a double definition.
'top military officers' is the first definition.
(top brass)
'thought of as bold?' is the second definition.
(as in the phrase 'bold as brass')
(Other definitions for brass that I've seen before include "Metal alloy" , "memorial in church" , "Family of wind instruments" , "An alloy; part of orchestra" , "Bold self-confidence" .)