One of those writing instruments with soft points (3)
I believe the answer is:
pen
'one of those writing instruments' is the definition.
I can't judge whether this definition defines the answer.
'with soft points' is the wordplay.
'with' means one lot of letters go next to another.
'soft' becomes 'p' (musical abbreviation for 'piano', soft).
'points' becomes 'en' (two compass points).
'p' next to 'en' is 'PEN'.
Can you help me to learn more?
(Other definitions for pen that I've seen before include "Shut up" , "Prison" , "Cage - bird" , "International writers's organisation" , "Writing implement" .)