That still doesn't tell me what is meant by "clusters of words."
I guess start by listing all the words you know that start with FL or that have FL in them somewhere.
Did you even go to onelook.com and look up FL* words?
http://www.onelook.com/?w=fl*&first=101
Be sure you list only the words that the kindergartener knows!!
Another way to think of this is to list words in "families" --
fly
flee
flight
flew
flown
flat
flatter
flattest
and so forth
Apologies, but I don't have access to previous questions or information posted at specific times. However, I'm here to help you with any homework questions you may have for a kindergarten level. Please go ahead and ask your question, and I'll do my best to assist you.