Happen to pass former electrical store on Parisian street (4,4)
I believe the answer is:
come true
'happen to pass' is the definition.
(if something comes true it happens)
'former electrical store on parisian street' is the wordplay.
'former electrical store' becomes 'Comet' (defunct electrical shop).
'on' means one lot of letters go next to another.
'parisian street' becomes 'rue' ('street' in French).
'comet'+'rue'='COME TRUE'
(Other definitions for come true that I've seen before include "Materialise" , "it's been realised" , "Happen in reality, as dreams may (4, 4)" , "More cute (anag)" , "Happen in the way that was hoped or forecast" .)