Post's cancelled preceding frost (6)
I believe the answer is:
office
'post's' is the definition.
(I've seen this before)
'cancelled preceding frost' is the wordplay.
'cancelled' becomes 'off' ('off' can be similar in meaning to 'cancelled').
'preceding' says to put letters next to each other.
'frost' becomes 'ice' ('ice' can be a synonym of 'frost').
'off'+'ice'='OFFICE'
(Other definitions for office that I've seen before include "Where many of us work" , "Firm" , "Workplace for clerks" , "Box ---, ticket agency" , "Position in government?" .)