Mint in silver wrapping I ate at the outset as defence (8)
I believe the answer is:
apologia
'defence' is the definition.
(apologia is a kind of defence)
'mint in silver wrapping i ate at the outset' is the wordplay.
'mint in' becomes 'polo' (I can't justify this - if you can you should give a lot more credence to this answer).
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'wrapping' means one lot of letters goes inside another.
'at the outset' indicates taking the first letters (the outset is the beginning).
The initial letter of 'ate' is 'a'.
'polo' inserted into 'ag' is 'apolog'.
'apolog'+'i'+'a'='APOLOGIA'
'as' is the link.
Can you help me to learn more?
(Other definitions for apologia that I've seen before include "Formal written defence of one's opinions/conduct" , "sort of defence" , "Written defence of one's conduct" , "Formal defence of belief or conduct" , "Written defence or vindication" .)