Especially a black protective coat Romeo discarded (5,3)
I believe the answer is:
above all
'especially' is the definition.
(thesaurus)
'a black protective coat romeo discarded' is the wordplay.
'a black' becomes 'ab' (I am not sure about this - if you are sure you should believe this answer much more).
'protective coat' becomes 'overall' (I've seen this before).
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'discarded' indicates named letters should be taken away.
'overall' with 'r' removed is 'oveall'.
'ab'+'oveall'='ABOVE ALL'
Can you help me to learn more?
(Other definitions for above all that I've seen before include "More than anything else" , "Most importantly" , "Shakespeare: 'This . . . . . . . ., to thine own self be true'" , "What 18 [EVEREST] is" , "Supremely" .)