Try to gain diamonds, beg an eccentric rock enthusiast (10)
I believe the answer is:
headbanger
'rock enthusiast' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'try to gain diamonds beg an eccentric' is the wordplay.
'try' becomes 'hear' (as in to try someone in court or hear their case).
'to gain' indicates putting letters inside.
'diamonds' becomes 'd' (abbreviation in bridge say).
'eccentric' is an anagram indicator.
'd'+'beg'+'an'='dbegan'
'dbegan' with letters rearranged gives 'dbange'.
'hear' placed around 'dbange' is 'HEADBANGER'.
Can you help me to learn more?
(Other definitions for headbanger that I've seen before include "crazy individual" , "Old music lover" , "Heavy-metal rock fan" .)