Impudence, sitting on mother’s last item of crockery (6)
I believe the answer is:
saucer
'item of crockery' is the definition.
(I've seen this before)
'impudence sitting on mother's last' is the wordplay.
'impudence' becomes 'sauce' (I've seen this before).
'sitting on mother's last' becomes 'r' (I can't justify this - if you can you should give a lot more credence to this answer).
'sauce'+'r'='SAUCER'
Can you help me to learn more?
(Other definitions for saucer that I've seen before include "See 1" , "Small dish, goes with cup" , "Piece of crockery, maybe flying" , "If flying, it would have alien pilots" , "flying, perhaps?" .)