Herb, one originally cultivated next to a colonnaded hall (8)
I believe the answer is:
basilica
'a colonnaded hall' is the definition.
(a basilica might have colonnades)
'herb one originally cultivated next' is the wordplay.
'herb' becomes 'basil' (basil is a herb).
'one' becomes 'a' (a thing is one thing).
'originally' means one lot of letters go next to another (some letters go before others).
'cultivated next' becomes 'ic' (I can't justify this - if you can you should give a lot more credence to this answer).
'a' put after 'ic' is 'ica'.
'basil'+'ica'='BASILICA'
'to' is the link.
Can you help me to learn more?
(Other definitions for basilica that I've seen before include "Large (Roman Catholic) church" , "Roman hall; church" , "Romanesque church" , "Roman building used for public administration" , "Roman public administration building Christian church" .)