Yes, that is playable
...and is worth 6 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"That" Definition
pronoun
According to what; insofar as: He never knew her, that I know of.
In, on, by, or with which: each summer that the concerts are performed.
The one, kind, or thing; something: She followed the calling of that which she loved.
Used as a relative pronoun to introduce a clause, especially a restrictive clause: the car that has the flat tire.
Used to emphasize the idea of a previously expressed word or phrase: He was fed up, and that to a great degree.
idiom
At that In addition; besides: lived in one room, and a small room at that.
At that Regardless of what has been said or implied: a long shot, but she just might win at that.
That is To explain more clearly; in other words: on the first floor, that is, the floor at street level.
adjective
Being the one further removed or less obvious: That route is shorter than this one.
Being the one singled out, implied, or understood: that place; those mountains.
Being the person, thing, or idea specified, mentioned, or understood.
Being the one specified .
adverb
To such an extent or degree: Is your problem that complicated?.
conjunction
Used to introduce a noun clause that is usually the subject or object of a verb or a predicate nominative: "That contemporary American English is exuberantly vigorous is undeniableā ( William Arrowsmith).
Used to introduce a subordinate clause modifying an adverb or adverbial expression: will go anywhere that they are welcome.
Used to introduce a subordinate clause stating a result, wish, purpose, reason, or cause: She hoped that he would arrive on time. He was saddened that she felt so little for him.
Used to introduce a subordinate clause that is joined to an adjective or noun as a complement: was sure that she was right; the belief that rates will rise soon.
Used to introduce an anticipated subordinate clause following the expletive it occurring as subject of the verb: It is true that dental work is expensive.