Up in heaven, egalitarian city with large lake (6)
I believe the answer is:
geneva
'large lake' is the definition.
(Lake Geneva is a lake)
'up in heaven egalitarian city' is the wordplay.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'in' indicates a hidden word.
'aveneg' is hidden in the letters of 'heaven egalitarian city'.
'aveneg' in reverse letter order is 'GENEVA'.
'with' is the link.
(Other definitions for geneva that I've seen before include "Swiss city housing the Red Cross headquarters" , "Swiss city, lake" , "Where to see Red Cross headquarters" , "European city" , "Swiss city - Dutch spirit" .)