18 Across, Arrest hooligan finally in derelict building (3,2) R?N ?? I had RUN IN, but this does not go with 19 Down.
19 Down, Normal, apparently to swallow sulphur in medicine (7) ??O?R?M
If 18 across is RUN IN then 19 down begins with an N to which I can find no words relating to the clue.