Saint with jewellery not right for oath (8)
I believe the answer is:
swearing
'oath' is the definition.
(synonyms)
'saint with jewellery not right for' is the wordplay.
'saint with' becomes 'sw' (this could be a standard abbreviation of which I'm unaware).
'jewellery' becomes 'earring' (earring is a kind of jewellery).
'not' suggests deleting specific letters.
'right for' becomes 'r' (I've seen this in other clues).
'earring' with 'r' taken away is 'earing'.
'sw'+'earing'='SWEARING'
Can you help me to learn more?
(Other definitions for swearing that I've seen before include "blue emissions?" , "Foul language" , "Taking an oath" , "Expressing annoyance" , "promising" .)