Somewhere to wait if the barn came apart (11)
I believe the answer is:
antechamber
'somewhere to wait' is the definition.
I can't tell whether this definition defines the answer.
'the barn came apart' is the wordplay.
'apart' indicates anagramming the letters (the word is broken apart).
'the'+'barn'+'came'='thebarncame'
'thebarncame' anagrammed gives 'ANTECHAMBER'.
'if' is the link.
Can you help me to learn more?
(Other definitions for antechamber that I've seen before include "Small entrance room" , "Small room before a larger one" , "External room" , "room outside another" , "Waiting room" .)