See one rat on entering block briefly (9)
I believe the answer is:
bishopric
'see' is the definition.
(both can mean a bishop's associated area)
'one rat on entering block briefly' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
'rat' could be 'shop' (both can mean to betray someone) and 'shop' is found in the answer.
This explanation may well be incorrect...
(Other definitions for bishopric that I've seen before include "position of a minister" , "Phobic sir (anag)" , "Episcopate" , "Church office" , "See - diocese" .)