Magazine featuring one central spread (6)
I believe the answer is:
paunch
'central spread' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'magazine featuring one' is the wordplay.
'magazine' becomes 'Punch' (historical satirical magazine).
'featuring' is an insertion indicator.
'one' becomes 'a' (a thing is one thing).
'punch' going around 'a' is 'PAUNCH'.
Can you help me to learn more?
(Other definitions for paunch that I've seen before include "Gut" , "Beer-belly" , "result of too much booze?" , "Protuberant stomach" , "Pot" .)