School hung maps showing growth in bogs (8)
I believe the answer is:
sphagnum
'growth in bogs' is the definition.
(type of moss that grows in bogs)
'school hung maps' is the wordplay.
'school' indicates an anagram (school can mean to improve or manipulate).
'hung'+'maps'='hungmaps'
'hungmaps' anagrammed gives 'SPHAGNUM'.
'showing' is the link.
(Other definitions for sphagnum that I've seen before include "Bog moss" , "Kind of moss that grows on bogs" , "Moss forming peat" , "Peat moss - push G-man (anag)" , "Plant of a genus including the peat mosses" .)