Is not at new post (7)
I believe the answer is:
station
'post' is the definition.
(a station is a post)
'is not at new' is the wordplay.
'new' indicates an anagram.
'is'+'not'+'at'='isnotat'
'isnotat' anagrammed gives 'STATION'.
(Other definitions for station that I've seen before include "E.g. Waverley, Waterloo" , "Building where service is based, fire or train" , "eg Temple Meads" , "Place - railway stop - HQ - standing" , "Train stop" .)