Swearing in English on the Bible to retain half the trade (7)
I believe the answer is:
abusive
'swearing in' is the definition.
Both the definition and answer are adjectives. Perhaps there's an association between them I don't understand?
'english on the bible to retain half the trade' is the wordplay.
'english on the bible' becomes 'ave' (I can't explain this - if you can you should give a lot more credence to this answer).
'to retain' means one lot of letters goes inside another.
'half the' means to take half the letters.
'trade' becomes 'business' (I've seen this before).
'business' with half the letters taken is 'busi'.
'ave' going around 'busi' is 'ABUSIVE'.
Can you help me to learn more?
(Other definitions for abusive that I've seen before include "Rude, insulting" , "Prone to mistreat" , "scathing" , "Insulting, being harshly critical or offensive" , "Given to hurling insults" .)