Dates and times ? Where you flying to/from ?
We land at 8am and fly back out at 1:30pm
Day of the week ? Weekends get busy...
On Saturday or Sunday you can take a free trolley from FLL to Riverfront and back to FLL , but if you have luggage not checked through you would have to pay to store it at Bags to Go in the baggage claim area. ( $7 /item I think). as it is not permitted on the Trolley. May not be worth your while for what is really a short time - probably only about four hours net after having to check in through security an hour before ( at minimum lines can be long) . The Trolley ride schedule may not fit your situation ....but it is one possibility for a weekend layover. There are not usually many good solutions.
You can google Sun Trolley Airport for details
It will be a Thursday
Inbound or outbound and which terminal?