Score 101 and total up (5)
I believe the answer is:
music
'score' is the definition.
(I've seen this in another clue)
'101 and total up' is the wordplay.
'101' becomes 'CI' (Roman numerals).
'and' means one lot of letters go next to another.
'total' becomes 'sum' (synonyms).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'ci'+'sum'='cisum'
'cisum' written backwards gives 'MUSIC'.
(Other definitions for music that I've seen before include "'Fled is that ---: do I wake or sleep?' (Keats)" , "'If ... be the food of love, play on'(Twelfth Night)" , "Melodious sound" , "Composed sounds" , "graces?" .)