Pawn diamonds before the old form returns for sport (3,6)
I believe the answer is:
ice hockey
'sport' is the definition.
(I know that ice hockey is a type of contact sport)
'pawn diamonds before the old form returns' is the wordplay.
'pawn' becomes 'hock' (hock can mean to pawn an item at a pawnbroker's).
'diamonds' becomes 'ice' (slang term for diamonds).
'before' is a charade indicator (letters next to each other).
'the old form' becomes 'ye' (I can't justify this - if you can you should believe this answer much more).
'returns' says the letters should be written in reverse.
'ye' reversed gives 'ey'.
'hock' put after 'ice' is 'icehock'.
'icehock'+'ey'='ICE-HOCKEY'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for ice hockey that I've seen before include "Violent sport, big in North America" , "Team game played with long sticks" , "Sport with puck" , "Game played by skaters with a puck" .)