Extremely rough gang shifting ring and diamond (5)
I believe the answer is:
rhomb
'diamond' is the definition.
(I know that diamond can be written as rhomb)
'extremely rough gang shifting ring' is the wordplay.
'extremely rough' becomes 'rho' (I can't explain this - if you can you should give a lot more credence to this answer).
'gang' becomes 'mob' (synonyms).
'shifting' indicates named letters should be taken away.
'ring' becomes 'O' (letter resembling a ring).
'mob' with 'o' taken out is 'mb'.
'rho'+'mb'='RHOMB'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for rhomb that I've seen before include "Equilateral parallelogram" , "Lozenge" , "Crystal shape" , "Figure on plane" , "Crystal with six faces having parallel edges" .)