Penny slept with tartan blanket (5)
I believe the answer is:
plaid
'blanket' is the definition.
(I know that plaid is a type of wearing blanket)
'penny slept with tartan' is the wordplay.
I cannot quite understand how this works, but
'penny' could be 'p' (short for pence) and 'p' is present in the answer.
The remaining letters 'laid' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for plaid that I've seen before include "Tartan twill cloth" , "Cloth for a Highlander" , "Scotsman's cloth" , "Tartan cloth, part of Highland dress" , "Check fabric" .)