Notice street in centre gets competitive advantage (4,5)
I believe the answer is:
head start
'competitive advantage' is the definition.
(I've seen this in another clue)
'notice street in centre' is the wordplay.
'notice' becomes 'ad' (both can mean an advertisement).
'street' becomes 'st' (abbreviation).
'in' means one lot of letters goes inside another.
'centre' becomes 'heart' (synonyms).
'ad'+'st'='adst'
'adst' placed within 'heart' is 'HEAD START'.
'gets' acts as a link.
(Other definitions for head start that I've seen before include "A good beginning using one's loaf" , "An early advantage for the star ad" , "It improves the chances of success!" , "Advantage gained by beginning early" , "'The advantage of beginning ahead of others (4,5)'" .)