>> Zeroing out the whole block containing it is the usual recipe.
Something like this worked for me in the past:
% dd bs=8k count=X < /dev/zero >> clog-file
I had to calculate X, because I usually had a situation with truncated
clog-file, and a failed attempt to read it from offset XYZ.
And I used pg_controldata to check on the block-size.
Mike.