Unfading Queen good with soldiers in uniform (9)
I believe the answer is:
evergreen
'unfading' is the definition.
(thesaurus)
'queen good with soldiers in uniform' is the wordplay.
'queen good with' becomes 'erg' (I can't justify this - if you can you should believe this answer much more).
'soldiers' becomes 're' (Royal Engineers).
'in' means one lot of letters goes inside another.
'uniform' becomes 'even' (both can mean equal or level).
'erg'+'re'='ergre'
'ergre' inserted inside 'even' is 'EVERGREEN'.
Can you help me to learn more?
(Other definitions for evergreen that I've seen before include "Ivy, perhaps" , "Durable" , "Having an enduring freshness" , "Leaves of holly and ivy are --" , "Having year-round foliage" .)