Equally calm, lake close to city (6)
I believe the answer is:
evenly
'equally' is the definition.
(I've seen this before)
'calm lake close to city' is the wordplay.
'calm' becomes 'even' (I've seen this before**).
'lake' becomes 'l'.
'close to' indicates one should take the final letters (the close/ending of).
The last letter of 'city' is 'y'.
'even'+'l'+'y'='EVENLY'
(Other definitions for evenly that I've seen before include "Equally or smoothly" , "In measured and level way" , "in a uniform way" , "In level or uniform manner" , "Material" .)