Joke about new crew (4)
I believe the answer is:
'crew' is the definition.
(I know that crew can be written as gang)
'joke about new' is the wordplay.
'joke' becomes 'gag' (a gag is a joke or witticism).
'about' indicates putting letters inside.
'new' becomes 'n' (abbreviation as in New Testament NT).
'gag' going around 'n' is 'GANG'.
(Other definitions for gang that I've seen before include "crowd" , "Go to the Scots" , "Working group or mob of hoodlums" , "Men working" , "Posse" .)