Clean some steps to protect Queen (7)
I believe the answer is:
sterile
'clean' is the definition.
(I've seen this before)
'some steps to protect queen' is the wordplay.
'some steps' becomes 'stile' (I've seen this in other clues).
'to protect' indicates putting letters inside.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'stile' placed around 'er' is 'STERILE'.
(Other definitions for sterile that I've seen before include "Free from living micro-organisms, absolutely clean" , "Like theatre" , "Unable to have children" , "Not producing offspring" , "Ineffective" .)