The most common and most likely answer to this crossword clue is the 8 letter word ANTIBODY
I've seen this crossword clue in The Times
A
N
T
I
B
O
D
Y
More clues leading to the result ANTIBODY
- Like ultra-spiritual type that offers response to disease?
- Penning notes on passing back, handyman defender
- Natural defence for small boy absorbing brief life in retrospect
- Independent group following worker’s protection against infection
- Stupidly obtain extremely dodgy protection against disease
- It’s counteractive and, boy, it’s volatile
- . Protein produced by indiscriminate hybridisation results in the birth of Irish
- Doctor obtained drug, released today — finally, a possible treatment for COVID
Buddy explains!

The straight part
We know that "that offers response to disease" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case that offers response to disease = antibody.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.
What does ANTIBODY mean?
ANTIBODY noun- A protein produced by B-lymphocytes that binds to a specific antigen.