Ein klares Feld oder ein freies Feld?

Question

Der Feind ist auf dem Rückzug. Wir haben ein klares Feld.

or should it be this?

Wir haben ein freies Feld.

DWDS provides examples of both.

Dann war Ihr Anfang aber auch nicht gut!) — Der diente nur der intellektuellen Bereinigung, damit wir auf einem klaren Feld debattieren.

Aus ihrer Sicht würden sie dadurch zwei Fliegen mit einer Klappe schlagen: Sie nähmen dem triumphierenden Iran seinen wichtigsten Verbündeten in der arabischen Welt und schafften gleichzeitig freies Feld für den Kampf gegen die Terrormilizen des "Islamischen Staates", die auch ihre Regime offen bedrohen.

Answer 1

These options are both possible and express what you want to say. The wonderful thing about language is that most of the times there are several ways to do something, several ways to skin a cat and different alternatives expressing the same, differing only in minor nuances.

Mastery of a language is (among other things) to select from these alternatives, with the primary goal (of what to say) down, depending on these finer nuances one wants to convey.

The limits of my language are the limits of my world.
_{L. Wittgenstein, Tractatus logico-philosophicus}

"frei" in this case means "without any obstacles, unimpeded", "klar" means the same. The "field" here is not a place to plant something but an area in general, like in e.g. "field of vision".

I would slightly prefer "freies Feld" here, but, first, this is my personal preference and doesn't make "klares Feld" wrong, second, with more context this evaluation might be subject to change and, third, nobody knows what you want to express as well as you yourself. So, it is ultimately your decision.

Answer 2

Those examples are different.

"Freies Feld" or "Schlachtfeld" (free battlefield) refers either to a literal place or figuratively to a conflict.

In the other example "klares Feld" means preparing a clear topic of a discussion. It doesn't mean that the discussion is finished and "won" by one side.