What those in 19 across are capable of to score (5)
I believe the answer is:
music
'score' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for music that I've seen before include "(Pleasant) sequence of sounds" , "Harmonious sounds" , "Composer's product" , "Harmonious sound (generally!)" , "Melody, harmony" .)