Quietly put down tartan (5)
I believe the answer is:
plaid
'tartan' is the definition.
(I know that tartan can be written as plaid)
'quietly put down' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'put down' becomes 'laid' (to lay something is to put it down somewhere).
'p'+'laid'='PLAID'
(Other definitions for plaid that I've seen before include "Tartan-pattern cloth" , "woollen cloth" , "Tartan cloth, part of Highland dress" , "piece of cloth" , "party in Wales" .)