Crossword Genius

Old capital has loyal citizens in for exercise (14)

Ross

I believe the answer is:

constantinople

I'm a little stuck... Click here to teach me more about this clue!

'old capital' is the definition.
The answer and definition can be both locations as well as being singular nouns.
I also know that 'old' relates to this answer.

'loyal citizens in for exercise' is the wordplay.
I cannot quite see how this works, but
'loyal' could be 'constant' and 'constant' is located in the answer.
'in' is within the answer.
This explanation may well be incorrect...

'has' is the link.

Can you help me to learn more?

(Other definitions for constantinople that I've seen before include "Old name of Istanbul" , "Former name of Istanbul" , "place that changed its name" , "Istanbul formerly" , "capital no longer used" .)

I've seen this clue in The Independent.
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