Coin used on state occasions (5)
I believe the answer is:
crown
'coin used on state occasions' is the definition.
'crown' can be an answer for 'coin' (I have seen 'Old coin ' mean 'crown' so perhaps 'coin' could also mean 'crown'). I'm not certain of the 'used on state occasions' bit.
'coin used on state occasions' is the wordplay.
'coin' becomes 'c'.
'used on state occasions' becomes 'rown' (I am not sure about this - if you are sure you should believe this answer much more).
'c'+'rown'='CROWN'
Can you help me to learn more?
(Other definitions for crown that I've seen before include "repair for damaged tooth" , "Old coin; top of tree" , "The sovereign" , "Coronet" , "Visible part of a tooth" .)