Force protecting king I put in danger (7)
I believe the answer is:
imperil
'put in danger' is the definition.
('imperil' can be a synonym of 'endanger')
'force protecting king i' is the wordplay.
'force' becomes 'impel' ('impel' can be a synonym of 'force'**).
'protecting' indicates putting letters inside.
'king' becomes 'r' (r is abbreviation for rex).
'r'+'i'='ri'
'impel' going around 'ri' is 'IMPERIL'.
(Other definitions for imperil that I've seen before include "Put in danger" , "Expose" , "Threaten, jeopardise" , "Endanger" , "Put at risk" .)