Platform for a meal outside a flat (6,3)
I believe the answer is:
launch pad
'platform' is the definition.
(launch pad is a kind of platform)
'a meal outside a flat' is the wordplay.
'meal' becomes 'lunch' (lunch is a kind of meal**).
'outside' means one lot of letters goes inside another.
'a flat' becomes 'pad' (person's home).
'a' going into 'lunch' is 'launch'.
'launch'+'pad'='LAUNCH PAD'
'for' is the link.
(Other definitions for launch pad that I've seen before include "platform" , "Where to use rocket" , "explorer's starting place" , "Good place to begin" , "Structure on which a rocket sits" .)