All welcome round at top floor flat, taking time out (4,5)
I believe the answer is:
open house
'out' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'all welcome round at top floor flat taking time' is the wordplay.
'all welcome round at' becomes 'o' (I am not sure about this - if you are sure you should believe this answer much more).
'top floor flat' becomes 'penthouse' (I've seen this before).
'taking' is a deletion indicator.
'time' becomes 't'.
'penthouse' with 't' removed is 'penhouse'.
'o'+'penhouse'='OPEN HOUSE'
Can you help me to learn more?
(Other definitions for open house that I've seen before include "Keep this to welcome all comers and guests" , "Situation where all are welcome" , "unbounded hospitality" , "Total hospitality" , "Invitation to all" .)