Capital of Louisiana in answer, one gathered? This isn't! (3,7)
I believe the answer is:
new orleans
'this isn't' is the definition.
The definition suggests a singular noun which matches the answer.
'capital of louisiana in answer one gathered?' is the wordplay.
'capital of' suggests taking the first letters.
'in' indicates putting letters inside.
'gathered?' indicates anagramming the letters (I've seen 'gathered' mean this).
The first letter of 'louisiana' is 'l'.
'answer'+'one'='answerone'
'answerone' anagrammed gives 'neworeans'.
'l' going within 'neworeans' is 'NEW ORLEANS'.
(Other definitions for new orleans that I've seen before include "City of Louisiana" , "port city in the south" , "US city" , "Devastated city" .)