Man first to recover without heroin: he used to score (6)
I believe the answer is:
mahler
'he used to score' is the definition.
The definition suggests a singular noun which matches the answer.
'man first to recover without heroin' is the wordplay.
'man' becomes 'male'.
'first to' suggests taking the first letters.
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'heroin' becomes 'h' (synonyms).
The first letter of 'recover' is 'r'.
'male'+'r'='maler'
'maler' enclosing 'h' is 'MAHLER'.
Can you help me to learn more?
(Other definitions for mahler that I've seen before include "Gustav -, Austrian symphonist" , "Gustave ......, noted Austrian composer-conductor" , "Austrian composer from Harlem?" , "Austrian symphonic composer, d. 1911" , "Harlem (anag) - composer" .)