Might war prisoner and monarch meet? (5)
I believe the answer is:
power
'might' is the definition.
('power' can be a synonym of 'might')
'war prisoner and monarch meet?' is the wordplay.
'war prisoner' becomes 'pow' (abbreviation for prisoner of war).
'and' is a charade indicator (letters next to each other).
'monarch meet?' becomes 'er' (I can't justify this - if you can you should give a lot more credence to this answer).
'pow'+'er'='POWER'
(Other definitions for power that I've seen before include "Government" , "Possession of controlling influence" , "Exponent" , "Physical force, ability" , "Supremacy, force" .)