Body snatcher ultimately found hiding in thicket (6)
I believe the answer is:
corpse
'body' is the definition.
(a corpse is a dead body)
'snatcher ultimately found hiding in thicket' is the wordplay.
'ultimately' indicates one should take the final letters.
'found hiding in' indicates putting letters inside.
'thicket' becomes 'copse' (synonyms).
The last letter of 'snatcher' is 'r'.
'r' placed within 'copse' is 'CORPSE'.
(Other definitions for corpse that I've seen before include "Dead body" , "Roof beam" , "Dead bodies" , "Cadaver, dead person" .)