He composed the last letter in the catalogue (5)
I believe the answer is:
liszt
'he composed the last' is the definition.
The definition suggests a singular noun which matches the answer.
'letter in the catalogue' is the wordplay.
'letter' becomes 'z'.
'in the' is an insertion indicator.
'catalogue' becomes 'list' (I've seen this before).
'z' going into 'list' is 'LISZT'.
Can you help me to learn more?
(Other definitions for liszt that I've seen before include "Hungarian piano virtuoso, d. 1886" , "Famous composer" , "Hungarian composer,d. 1886" , "He scored" , "Hungarian composer, d. 1886" .)