Lad secures a large reception room (5)
I believe the answer is:
salon
'reception room' is the definition.
(I've seen this in another clue)
'lad secures a large' is the wordplay.
'lad' becomes 'son' (lad can informally mean a young boy).
'secures' is an insertion indicator.
'large' becomes 'L' (eg in clothes sizes).
'a'+'l'='al'
'son' placed around 'al' is 'SALON'.
(Other definitions for salon that I've seen before include "Loans for elegant guest room" , "Large reception room" , "Reception room - social gathering" , "social event" , "Elegant room - for hairdresser?" .)