Almost see a politician building (11)
I believe the answer is:
observatory
'building' is the definition.
(observatory is a kind of building)
'almost see a politician' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'see' becomes 'observe' (I've seen this before).
'politician' becomes 'tory' (term for a Conservative Party politician).
'observe' with its last letter taken off is 'observ'.
'observ'+'a'+'tory'='OBSERVATORY'
(Other definitions for observatory that I've seen before include "Building used for astronomy" , "Where wise men scan the heavens" , "E.g. Jodrell Bank" , "Astronomy centre" , "Building equipped to view the heavens" .)