Material lodged underneath piano (5)
I believe the answer is:
plaid
'material' is the definition.
(I know that plaid is a type of material)
'lodged underneath piano' is the wordplay.
'lodged' becomes 'laid'.
'underneath' says to put letters next to each other (in a down clue, some letters go under others).
'piano' becomes 'p' (musical abbreviation).
'laid' put after 'p' is 'PLAID'.
(Other definitions for plaid that I've seen before include "woollen cloth" , "Tartan twilled cloth" , "material" , "Scots cloth - Welsh party" , "piece of cloth" .)