Enter a clue or pattern or both:
The ClueLeaked slowly (6 letter answer)
NotesThe answer SEEPED is seen occasionally, appearing about once every 650 puzzles.
Permeated, with "into"
Leaked almost imperceptibly
Came through the wall, maybe
DefinitionSEEP as a verb:
1. (seep, ooze) = pass gradually or leak through or as if through small openings