See City of Light stifling a sigh occasionally (7)
I believe the answer is:
'see city' is the definition.
(historical site of the See of Glasgow)
'light stifling a sigh occasionally' is the wordplay.
'light' becomes 'glow' (glow is a kind of light**).
'stifling' indicates putting letters inside.
'occasionally' means one should take alternating letters.
The alternating letters of 'sigh' are 'sg'.
'glow' going around 'asg' is 'GLASGOW'.
'of' acts as a link.
(Other definitions for glasgow that I've seen before include "City of bad low gags" , "Scots city" , "Scottish metropolis" , "Where to find Sauchiehall Street" , "European City of Culture, 1990" .)