If you can't spell too well, don't throw it in! (5)
I believe the answer is:
towel
'in' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for towel that I've seen before include "Drier" , "Piece of absorbent cloth or paper for drying" , "what sweater needs?" , "Dryer" , "Bathroom item" .)