Score century inside the ground (4)
I believe the answer is:
etch
'score' is the definition.
(thesaurus)
'century inside the ground' is the wordplay.
'century' becomes 'c' (common abbreviation).
'inside' is an insertion indicator.
'ground' indicates an anagram (grind the letters ).
'the' with letters rearranged gives 'eth'.
'c' going inside 'eth' is 'ETCH'.
(Other definitions for etch that I've seen before include "Carve into metal with acid" , "Carve into surface, impress deeply" , "Make deep lines" , "What most engravers presumably find easy to do" , "Make picture by engraving metal" .)