Cat is almost grave (3)
I believe the answer is:
tom
'cat' is the definition.
(a tom is a male cat)
'almost grave' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'grave' becomes 'tomb' (synonyms).
'tomb' with its final letter taken off is 'TOM'.
'is' acts as a link.
(Other definitions for tom that I've seen before include "What Dick Whittington had" , "Waits, perhaps" , "Edgar's Poor disguise (Lear)" , "queen's consort?" , "Boy running off with pig" .)