Container some felt to be upside down (6)
I believe the answer is:
bottle
'container' is the definition.
(I know that bottle is a container)
'some felt to be upside down' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'upside down' says the letters should be written backwards.
'elttob' is hidden in the letters of 'felt to be'.
'elttob' written backwards gives 'BOTTLE'.
(Other definitions for bottle that I've seen before include "It keeps drink" , "Glass container - firmness of resolve" , "Pitcher perhaps" , "Nerve (sl.)" , "Type of marine mammal" .)