Top Tory admitting centre of Britain is closed (8)
I believe the answer is:
airtight
'is closed' is the definition.
'top tory admitting centre' is the wordplay.
'top' becomes 'ai' (I've seen this in other clues).
'tory' becomes 'r' (abbreviation for right).
'admitting centre' becomes 'tight' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ai'+'r'+'tight'='AIRTIGHT'
'of britain' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for airtight that I've seen before include "beyond question" , "Impenetrable" , "(Of a defence) having no weaknesses" , "Totally sealed" , "securely sealed" .)