Pattern involving a gangster and a small cup-shaped structure (7)
I believe the answer is:
calycle
'cup-shaped structure' is the definition.
(I've seen this before)
'pattern involving a gangster' is the wordplay.
'pattern' becomes 'cycle' (I can't justify this - if you can you should give a lot more credence to this answer).
'involving' means one lot of letters goes inside another.
'a gangster' becomes 'al' (Al Capone).
'cycle' enclosing 'al' is 'CALYCLE'.
'and a small' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Another definition for calycle that I've seen is " cup-shaped structure".)