Disappointing score upset trendy musical in the end (3)
I believe the answer is:
nil
'disappointing score' is the definition.
'nil' can be an answer for 'score' (I've seen this before). I am not sure about the 'disappointing' bit.
'upset trendy musical in the end' is the wordplay.
'upset' says the letters should be written in reverse.
'trendy' becomes 'in' ('in' can mean fashionable).
'in the end' says to take the final letters.
The last letter of 'musical' is 'l'.
'in' in reverse letter order is 'ni'.
'ni'+'l'='NIL'
Can you help me to learn more?
(Other definitions for nil that I've seen before include "Nothing - in Latin" , "Zero, no score" , "Lacking value" , "Nothing, no value" , "You get nothing" .)