Leaping into little retail outlet? No, a big one! (8,4)
I believe the answer is:
shopping mall
'retail outlet? no a big one' is the definition.
I can't tell whether this definition defines the answer.
'leaping into little' is the wordplay.
'leaping' becomes 'hopping' (hopping is a kind of leaping).
'into' indicates putting letters inside.
'little' becomes 'small' (synonyms).
'hopping' placed inside 'small' is 'SHOPPING MALL'.
(Other definitions for shopping mall that I've seen before include "Commercial precinct" , "retail centre" .)