Led army, moving to protect king — obviously (8)
I believe the answer is:
markedly
'obviously' is the definition.
(thesaurus)
'led army moving to protect king' is the wordplay.
'moving' indicates anagramming the letters.
'to protect' indicates putting letters inside.
'king' becomes 'k'.
'led'+'army'='ledarmy'
'ledarmy' is an anagram of 'maredly'.
'maredly' going around 'k' is 'MARKEDLY'.
(Other definitions for markedly that I've seen before include "In a clearly noticeable manner" , "Prominently, distinctly" .)