Long and thin piece of wood, not soft (4)
I believe the answer is:
lank
'long and thin' is the definition.
(I've seen this before)
'piece of wood not soft' is the wordplay.
'piece of wood' becomes 'plank'.
'not' is a deletion indicator.
'soft' becomes 'p' (musical abbreviation for 'piano').
'plank' with 'p' removed is 'LANK'.
(Other definitions for lank that I've seen before include "Lean and limp" , "Lustreless" , "Limp, lifeless (hair)" , "Flabby" , "Long, thin and often limp" .)