In the main, might augur set about a captive? (3,5)
I believe the answer is:
sea power
'in the main might' is the definition.
I can't tell whether this definition defines the answer.
'augur set about a captive?' is the wordplay.
'augur' becomes 'seer' (I've seen this in another clue).
'set about' indicates putting letters inside.
'captive?' becomes 'POW' (prisoner of war).
'a'+'pow'='apow'
'seer' enclosing 'apow' is 'SEA-POWER'.
Can you help me to learn more?
(Other definitions for sea power that I've seen before include "threat, in the main" , "Naval strength" , "Ability to rule the waves?" .)