Bent rich mob like diamonds (7)
I believe the answer is:
rhombic
'like diamonds' is the definition.
(I've seen this before)
'bent rich mob' is the wordplay.
'bent' indicates an anagram.
'rich'+'mob'='richmob'
'richmob' anagrammed gives 'RHOMBIC'.
(Other definitions for rhombic that I've seen before include "shaped like a diamond" , "Like a parallelogram with equal sides" , "Like diamonds" , "diamond-shaped" , "Quadrilateral-shaped with equal sides" .)