Managed to contain party element (5)
I believe the answer is:
radon
'element' is the definition.
(radon is a kind of element)
'managed to contain party' is the wordplay.
'managed' becomes 'ran' (I've seen this before).
'to contain' means one lot of letters goes inside another.
'party' becomes 'do' (do is a kind of party).
'ran' going around 'do' is 'RADON'.
(Other definitions for radon that I've seen before include "Inert gas that occurs naturally" , "Naturally occurring inert gas" , "A radioactive gas, symbol Rn" , "gets no reaction" , "Radioactive gas, linked to granite" .)