King in fit state (5)
I believe the answer is:
argue
'state' is the definition.
(thesaurus)
'king in fit' is the wordplay.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'in' means one lot of letters goes inside another.
'fit' becomes 'ague' (I've seen this before).
'r' placed into 'ague' is 'ARGUE'.
(Other definitions for argue that I've seen before include "Quarrel or disagree" , "Disagree heatedly" , "Wrangle" , "Contend with reasoning" , "Exchange heated views" .)