Security device one has on the piano? (4)
I believe the answer is:
hasp
'security device' is the definition.
'hasp' can be an answer for 'device' (hasp is a kind of device). I am not sure about the 'security' bit.
'one has on the piano?' is the wordplay.
'on' says to put letters next to each other.
'the piano?' becomes 'p'.
'has'+'p'='HASP'
Can you help me to learn more?
(Other definitions for hasp that I've seen before include "catch" , "This part of fastening device" , "Door latch" , "part of a lock" , "Hinged fastener for door or lid" .)