Take me dancing with gangster, ultimately becoming part of mob (7)
I believe the answer is:
meerkat
'part of mob' is the definition.
(mob is the collective noun for meerkats)
'take me dancing with gangster ultimately' is the wordplay.
'dancing with' indicates anagramming the letters.
'ultimately' suggests the final letters.
The last letter of 'gangster' is 'r'.
'take'+'me'='takeme'
'takeme' anagrammed with 'r' gives 'MEERKAT'.
'becoming' is the link.
(Other definitions for meerkat that I've seen before include "Small mongoose of southern Africa" , "Strange tee mark made by the four-toed animal" , "Small southern African mongoose" , "Mongoose-like animal" , "Small southern African mammal" .)