He has a living putting union extremes on a record (7)

'he has a living' is the definition.
The definition suggests a singular noun which matches the answer.

'union extremes on a record' is the wordplay.
'extremes' means to remove the middle letters.
'on' means one lot of letters go next to another.
'record' becomes 'list' (list is a type of record).
'union' with its centre removed is 'un'.
'un'+'a'+'list'='UNALIST'

'putting' acts as a link.

Can you help me to learn more?