Take on appropriate accommodation for party (5)
I believe the answer is:
adopt
'take on' is the definition.
(synonyms)
'appropriate accommodation for party' is the wordplay.
'appropriate' becomes 'apt' (synonyms).
'accommodation for' indicates putting letters inside (some letters accommodate others).
'party' becomes 'do' (do is a kind of party).
'apt' placed around 'do' is 'ADOPT'.
(Other definitions for adopt that I've seen before include "choose as candidate" , "Foster" , "Embrace" , "Assume (attitude)" , "Formally approve" .)