Nasty geezer buries last of treasure (4)
I believe the answer is:
mean
'nasty' is the definition.
(similar in meaning)
'geezer buries last of treasure' is the wordplay.
'geezer' becomes 'man' (I've seen this before).
'buries' means one lot of letters goes inside another.
'last of' suggests the final letters.
The last letter of 'treasure' is 'e'.
'man' going around 'e' is 'MEAN'.
(Other definitions for mean that I've seen before include "Name for being tight-fisted" , "Signify; tight" , "Signify; average" , "Import" , "mercenary" .)