I recently started trading the TF and wondering if there is an instrument that correlates.

Thanks in advance.

TF correlates well with S&P midcap index (99% correlation over last 5 years), Russell 1000 index(98%), ES(97%), NQ(96%). (Ref: csidata)
Other instruments are Soybean, corn, ASX index, NZD dollar with around 88-92%correlation.
But if you are looking for a cue for direction from another correlated instrument, then SP midcap could be the one. But one should take the cue from thinner instrument and trade the thicker or more liquid instrument.

Perfect. Thanks so much.

TF is the futures contract for the Russell 2000 index. IWM is the ETF for the same index and moves with the TF almost perfectly except for the four times a year when the ETF goes ex-dividend. The CBOE also has RUT options that are based on the Russell 2000 index.