Body in tree found by trappers' leader (6)
I believe the answer is:
planet
'body' is the definition.
(I have seen 'Celestial body' mean 'planet' so perhaps 'body' could also mean 'planet')
'tree found by trappers' leader' is the wordplay.
'tree' becomes 'plane tree' (plane is a type of tree).
'found by' means one lot of letters go next to another.
'leader' says to take the initial letters.
The initial letter of 'trappers' is 't'.
'plane'+'t'='PLANET'
'in' is the link.
(Other definitions for planet that I've seen before include "Celestial body orbiting around a star" , "Venus, for example" , "Is Pluto one?" , "Substantial heavenly body" , "Eg, a ruby" .)