One section respectively (6)
I believe the answer is:
apiece
'respectively' is the definition.
(thesaurus)
'one section' is the wordplay.
'one' becomes 'a' (a thing is one thing).
'section' becomes 'piece' (I've seen this before).
'a'+'piece'='APIECE'
(Other definitions for apiece that I've seen before include "for everyone" , "A head" , "Per person" , "For or by each one of group" .)