A sweet friend has run home with a key (7)
I believe the answer is:
praline
'a sweet' is the definition.
(praline is a kind of sweet)
'friend has run home with a key' is the wordplay.
'friend' becomes 'pal' (pal can mean a friend).
'has' indicates putting letters inside.
'run' becomes 'r' (cricket abbreviation).
'home' becomes 'in' ('he's home' can mean 'he's in').
'with a key' becomes 'e' (I am not sure about this - if you are sure you should believe this answer much more).
'pal' placed around 'r' is 'pral'.
'pral'+'in'+'e'='PRALINE'
Can you help me to learn more?
(Other definitions for praline that I've seen before include "Confection made with crushed nuts" , "Substance made of nuts boiled in sugar, used to fill chocolates" , "Filling for chocolates made by boiling nuts in sugar" , "Sweet stuff" , "French confection" .)