Hold good epitaph (4)
I believe the answer is:
grip
'hold' is the definition.
(I know that hold can be written as grip)
'good epitaph' is the wordplay.
'good' becomes 'g' (abbreviation).
'epitaph' becomes 'RIP' (rest in peace).
'g'+'rip'='GRIP'
(Other definitions for grip that I've seen before include "Clench" , "Hold hard" , "Hold firmly; travelling bag" , "Seize interest" , "Baggage - hold" .)