Sovereign put in danger keeps close to Camilla (8)
I believe the answer is:
imperial
'sovereign' is the definition.
(I've seen this before)
'put in danger keeps close to camilla' is the wordplay.
'put in danger' becomes 'imperil' (synonyms).
'keeps' means one lot of letters goes inside another (inserted letters are kept inside).
'close to' says to take the final letters (the close/ending of).
The last letter of 'camilla' is 'a'.
'imperil' enclosing 'a' is 'IMPERIAL'.
(Other definitions for imperial that I've seen before include "Magnificent; mint --" , "Mint --, sweet" , "Of an empire or its ruler" , "measure" , "Relating to empire" .)