The speed that's associated with the score (5)
I believe the answer is:
tempo
'the speed' is the definition.
(I've seen this before)
'associated with the score' is the wordplay.
'associated with' means one lot of letters go next to another.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'score' becomes 'empo' (I can't explain this - if you can you should give a lot more credence to this answer).
't'+'empo' is 'TEMPO'.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for tempo that I've seen before include "Musical beat or rhythm" , "Pace of a musical piece" , "Pace - pacing" , "Speed at which piece of music is played" , "Rate and rhythm in music" .)