Poem on place of learning describes everything (8)
I believe the answer is:
universe
'describes everything' is the definition.
(I know that Universe main subject the universe)
'poem on place of learning' is the wordplay.
'poem' becomes 'verse' (verse is a kind of poem).
'on' means one lot of letters go next to another.
'place of learning' becomes 'uni' (university).
'verse' after 'uni' is 'UNIVERSE'.
(Other definitions for universe that I've seen before include "The whole of everything" , "sphere of activity" , "Edible crustacean" , "Everything, really" , "all we know?" .)