Gangster’s work activity recalled - it involves death-dealing (9)

'gangster's' is the definition.
(goodfellas can mean gangsters)

'work activity recalled it involves death-dealing' is the wordplay.
'work' becomes 'go' (synonyms).
'activity' becomes 'ado' (ado can mean commotion or activity).
'recalled' says the letters should be written in reverse.
'it involves' means one lot of letters goes inside another.
'death-dealing' becomes 'fell' (fell can mean deadly, as in 'one fell swoop').
'ado' reversed gives 'oda'.
'oda' enclosing 'fell' is 'odfella'.
'go'+'odfella'='GOODFELLA'