The term 'Diamond Deal' is a phrase used to describe a particular type of TRADE or transaction. The crossword solutions for this term are 'TRADE' (5 letters) and 'twinbill' (8 letters). A TRADE is an exchange of goods or services between two or more parties, while a twinbill is a doubleheader, or two games played back-to-back by the same teams in the same venue. Therefore, the term 'Diamond Deal' could refer to a TRADE involving two games or events.