Peat moss (8)
I believe the answer is:
sphagnum
'peat moss' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for sphagnum that I've seen before include "Peat moss - push G-man (anag)" , "Type of moss" , "Pale peat moss -- human GPs (anag)" , "Kind of moss that grows on bogs" , "Peat moss plant" .)