Understanding grave's initial epitaph (4)
I believe the answer is:
grip
'understanding' is the definition.
(I've seen this in another clue)
'grave's initial epitaph' is the wordplay.
'initial' indicates taking the first letters.
'epitaph' becomes 'RIP' (rest in peace).
The initial letter of 'graves' is 'g'.
'g'+'rip'='GRIP'
(Other definitions for grip that I've seen before include "Engage" , "Grasp tightly" , "Hold hard" , "Stagehand" , "Secure" .)