Close to grave and terrible danger — get ready! (2,5)
I believe the answer is:
en garde
'get ready' is the definition.
(phrase used in fencing)
'close to grave and terrible danger' is the wordplay.
'close to' suggests the final letters (the close/ending of).
'and' says to put letters next to each other.
'terrible' indicates an anagram.
The last letter of 'grave' is 'e'.
'danger' anagrammed gives 'ngarde'.
'e'+'ngarde'='EN GARDE'
(Other definitions for en garde that I've seen before include "Fencer's warning cry" , "Get ready to fence" , "Words of warning" , "French opening position in fencing - protect yourself" , "(In fencing) in a defensive stance" .)