Party poster moved around threshold (8)
I believe the answer is:
doorstep
'threshold' is the definition.
(synonyms)
'party poster moved around' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'moved' is an anagram indicator.
'around' indicates putting letters inside.
'poster' anagrammed gives 'orstep'.
'do' put inside 'orstep' is 'DOORSTEP'.
(Other definitions for doorstep that I've seen before include "To conduct house-to-house interviews" , "Sill at threshold" , "substantial amount of bread" , "slab at threshold" , "go canvassing" .)