Gnome always covered in grass (6)
I believe the answer is:
saying
'gnome' is the definition.
(thesaurus)
'always covered in grass' is the wordplay.
'always' becomes 'ay'.
'covered in' means one lot of letters goes inside another.
'grass' becomes 'sing' (I've seen this in other clues).
'ay' put inside 'sing' is 'SAYING'.
(Other definitions for saying that I've seen before include "Adage, maxim" , "Epigram" , "Saw" , "Speaking of maxim?" , "Motto" .)