Human going to ground around lake (9)
I believe the answer is:
earthling
'human' is the definition.
(earthling is a kind of human)
'going to ground around lake' is the wordplay.
'going to ground' becomes 'earthing' (I've seen this before).
'around' is an insertion indicator.
'lake' becomes 'L' (geographical abbreviation).
'earthing' enclosing 'l' is 'EARTHLING'.
(Other definitions for earthling that I've seen before include "Man of the world" , "Human being (sci-fi)" , "sci-fi character" , "man so to be called from space?" .)