Crab finally consumed and vanquished (6)
I believe the answer is:
beaten
'vanquished' is the definition.
(beating is a kind of vanquishing)
'crab finally consumed' is the wordplay.
'finally' suggests the final letters.
'consumed' becomes 'eaten' ('eaten' can be similar in meaning to 'consumed').
The final letter of 'crab' is 'b'.
'b'+'eaten'='BEATEN'
'and' is the link.
(Other definitions for beaten that I've seen before include "Defeated - thrashed" , "Thrashed or whisked" , "Defeated - whipped" , "Baffled" , "Vanquished" .)