Overthrow Crown with short defence (6)
I believe the answer is:
topple
'overthrow' is the definition.
(I've seen this before)
'crown with short defence' is the wordplay.
'crown with' becomes 'top' ('top' can be a synonym of 'crown'. I am not sure about the 'with' bit.**).
'short' means to remove the last letter.
'defence' becomes 'plea' (plea is a kind of defence).
'plea' with its last letter taken away is 'ple'.
'top'+'ple'='TOPPLE'
Can you help me to learn more?
(Other definitions for topple that I've seen before include "Knock off perch" , "dethroned" , "Overbalance and fall headlong" , "(Cause to) tip over" , "Overthrow, cause to fall" .)