Take some glen in, gradually finding old city (9)
I believe the answer is:
leningrad
'old city' is the definition.
(former name of St Petersburg)
'take some glen in gradually' is the wordplay.
'take some' says the answer is hidden in the clue.
'LENINGRAD' is hidden in the letters of 'glen in gradually'.
'finding' is the link.
(Other definitions for leningrad that I've seen before include "St Petersburg formerly" , "Name of St Petersburg from 1924 to 1991" , "St Petersburg before nineteen ninety one" , "Soviet city now St Petersburg" , "Former name of city" .)