The most common and most likely answer to this crossword clue is the 9 letter word DISSENTER
I've seen this crossword clue in The Sunday Telegraph
D
I
S
S
E
N
T
E
R
More clues leading to the result DISSENTER
- Nonconformist unsettled residents
- Nonconformist to pour scorn on record
- Protestor will infiltrate Norfolk town first
- Maybe Protestant doctor desires to retain 24s
- Criticise record of Nonconformist
- Protester putting rubbish on register
- Show lack of respect for record set down by non-establishment figure
- Nonconformist duke is despatched by the Queen
- Nonconformist‘s insult put on record
- Rebel is transported East in doctor’s care
Buddy explains!

The straight part
We know that "person expressing resistance" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case person expressing resistance = dissenter.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 DISSENTER mean?
DISSENTER noun- Someone who dissents (disagrees), especially from an established church.