Bognor extension? Test records kept here (8)
I believe the answer is:
registry
'records kept here' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'bognor extension? test' is the wordplay.
I cannot really understand how this works, but
'test' could be 'try' (synonyms) and 'try' is found in the answer.
The remaining letters 'regis' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for registry that I've seen before include "Place where written documents or records are kept" , "Place of record" , "Official written record of names, events etc" , "Place to keep records" , "Place where recorded list is kept" .)