How would you write:
"This is the symbol for spades in a deck of playing cards"
The following is not a very good translation:
Это символ пики в колоде игральных карт.
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If you just want to define the symbol, I'd say:
Это символ масти пик.
Это символ пиковой масти.
You don't need to mention the deck of playing cards, as the word "масть" already makes the meaning unambiguous.
Also, you might consider using the word "значок" instead of "символ", especially if you're talking about typesetting symbols (from some font, etc), as opposed to a large painting of this symbol, for instance.
It's hard to say without context. But it is possible to say "Пики - один из четырех символов в колоде игральных карт".
That way, you avoid the awkward ambiguity associated with the translation of символ пики (символ пики = symbol of playing cards in the nominative / symbol of weapons in the singular, символ пик = symbol of playing cards in the genitive / symbol of weapons in the plural).