Usually, for a grave, carved, one holds (2,7)
I believe the answer is:
on average
'usually' is the definition.
(I've seen this before)
'a grave carved one holds' is the wordplay.
'carved' indicates anagramming the letters.
'holds' means one lot of letters goes inside another.
'a'+'grave'='agrave'
'agrave' anagrammed gives 'averag'.
'averag' going into 'one' is 'ON AVERAGE'.
'for' is the link.
(Other definitions for on average that I've seen before include "typically speaking" , "Generally" , "Usually" .)