One will remain cool and play diamonds first (8)
I believe the answer is:
icefield
'one will remain cool' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'play diamonds first' is the wordplay.
'play' becomes 'field' (fielding is a kind of playing).
'diamonds' becomes 'ice' (slang term for diamonds).
'first' is a charade indicator (letters next to each other).
'field' after 'ice' is 'ICEFIELD'.
'and' is the link.
Can you help me to learn more?
(Another definition for icefield that I've seen is " a very inhospitable place".)