Insist on formalities and stay on your feet, my encore is fabulous! (5,2,8)
I believe the answer is:
stand on ceremony
'insist on formalities and stay on your' is the definition.
I know nothing about this answer so I cannot tell whether this works.
'feet my encore is fabulous' is the wordplay.
'feet' becomes 'standon' (I can't explain this - if you can you should believe this answer much more).
'is fabulous' indicates an anagram (a dramatic or fabulous change to the letters).
'my'+'encore'='myencore'
'myencore' with letters rearranged gives 'ceremony'.
'standon'+'ceremony'='STAND ON CEREMONY'
Can you help me to learn more?
(Other definitions for stand on ceremony that I've seen before include "observe formalities" , "act formally" , "Insist on the observance of formalities" , "Be overformal" , "Be formal" .)