The most common and most likely answer to this crossword clue is the 5 plus 5 letter word BLOOD DONOR
I've seen this crossword clue in Independent
B
L
O
O
D
D
O
N
O
R
More clues leading to the result BLOOD DONOR
- What one would give to be involved in the group matches!
- Dandy fellow — or one whose contribution is vital
- Gore, the presenter: “Here’s a classic comedy episode”
- Contributor of vital liquid assets deposited in bank
- He contributes to the liquid assets of a bank
- Pablo odd on ordering sandwiches for the life-giver
Buddy explains!
The straight part
We know that "one whose contribution is vital" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one whose contribution is vital = blood donor.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.