Witty remark on tomb out of place (3,3)
I believe the answer is:
bon mot
'witty remark' is the definition.
(I've seen this before)
'on tomb out of place' is the wordplay.
'out of place' indicates an anagram.
'on'+'tomb'='ontomb'
'ontomb' is an anagram of 'BON MOT'.
(Other definitions for bon mot that I've seen before include "term of French, it's appropriate to say" , "Appropriate word or expression - in France" , "Witticism" , "quip" , "Witty words" .)